Integration of light signaling with photoperiodic flowering and circadian rhythm

Plants become photosynthetic through de-etiolation, a developmental process regulated by red/far-red light-absorbing phytochromes and blue/ultraviolet A light-absorbing cryptochromes. Genetic screens have identified in the last decade many far-red light signaling mutants and several red and blue light signaling mutants, suggesting the existence of distinct red, far-red, or blue light signaling pathways downstream of phytochromes and cryptochromes. However, genetic screens have also identified mutants with defective de-etiolation responses under multiple wavelengths. Thus, the opti- mal de-etiolation responses of a plant depend on coordination among the different light signaling pathways. This review intends to discuss several recently identified signaling components that have a potential role to integrate red, far-red, and blue light signalings. This review also highlights the recent discoveries on proteolytic degradation in the desensitization of light signal transmission, and the tight connection of light signaling with photoperiodic flowering and circadian rhythm. Studies on the controlling mechanisms of de-etiolation, photoperiodic flowering, and circadian rhythm have been the fascinating topics in Arabidopsis research. The knowledge obtained from Arabidopsis can be readily applied to food crops and ornamental species, and can be contributed to our general understanding of signal perception and transduction in all organisms.

Flower Development and Photoperiodic Control of Flowering in Rice

Floral transition,which is referred to as a plant＇s transition from vegetative stage to reproductive stage,is considered to be a critical developmental switch in higher plants,for a timely flowering is a major factor of reproductive success.Endogenous and environmental cues,such as photoperiod,light quality,plant hormones concentrations and temperature,provide information to the plants whether the environment is favorable for flowering.These cues promote,or prevent,flowering through a complex genetic network,mediated by a careful orchestration of temporal and spatial gene expression.One of such cues is photoperiod.Rice（Oryza sativa L.） serves as a powerful model species for the understanding of flowering in higher plants,including flower development and photoperiodic control of flowering.In this review,we overviewed and discussed the flower development and its model.We also overviewed the photoperiodic pathways in rice flowering control,and summarized the pathways at molecular level.

Seasonal photoperiodic influence of pineal melatonin on hypothalamic-pituitary-adrenal axis-hippocampal-receptor in male rats

Background: Based on the effect of seasonal changes on human visceral function, this study investigated the impact of seasonal photoperiod of the pineal body on hypothalamic-pituitary-adrenal axis-hippocampal-receptor in rats, aiming to reveal the mechanism by which pineal gland melatonin regulates the seasonal secretion of hippocampal neurotransmitters.Methods: Vernal equinox, summer solstice, autumn equinox, and winter solstice were selected as four experimental time points, and rats were randomly divided into normal control group, sham operation group, and pinealectomized group. The seasonal changes in corticotropin-releasing hormone(CRH),adrenocorticotropic hormone(ACTH), corticosterone, hypothalamic melatonin receptor(MTR), and hippocampal corticosterone receptor(CORTR) were examined by enzyme-linked immunosorbent assay.Results: Comparing the same group between different seasons, we showed that in the normal control group, CRH, ACTH, corticosterone, and MTR were higher, while CORTR was lower in autumn and winter than in spring(all P <.05). Compared with the normal control group, the pinealectomized group showed higher levels of corticosterone(P =.01), MTR(P =.01), and CORTR(P =.03) during spring;reduced levels of MTR and CORTR(both P <.001) during summer;higher levels of ACTH(P =.001) and MTR(P <.001),and lower levels of CRH(P =.001), corticosterone(P <.001), and CORTR(P =.003) during autumn;and lower levels of CRH(P <.001) and MTR(P =.004), and higher level of ACTH(P <.001) in winter.Conclusions: Seasonal photoperiod acts on the pineal gland to secrete different levels of melatonin,resulting in seasonal changes in the hypothalamic-pituitary-adrenal axis-hippocampal-receptor, which may be the pathophysiological basis for the onset of seasonal affective disorder.

Photoperiodic flowering in Arabidopsis:Multilayered regulatory mechanisms of CONSTANS and the florigen FLOWERING LOCUS T

The timing of flowering affects the success of sexual reproduction.This developmental event also determines crop yield,biomass,and longevity.Therefore,this mechanism has been targeted for improvement along with crop domestication.The underlying mechanisms of flowering are highly conserved in angiosperms.Central to these mechanisms is how environmental and endogenous conditions control transcriptional regulation of the FLOWERING LOCUS T(FT)gene,which initiates floral development under long-day conditions in Arabidopsis.Since the identification of FT as florigen,efforts have been made to understand the regulatory mechanisms of FT expression.Although many transcriptional regulators have been shown to directly influence FT,the question of how they coordinately control the spatiotemporal expression patterns of FT still requires further investigation.Among FT regulators,CONSTANS(CO)is the primary one whose protein stability is tightly controlled by phosphorylation and ubiquitination/proteasome-mediated mechanisms.In addition,various CO interaction partners,some of them previously identified as FT transcriptional regulators,positively or negatively modulate CO protein activity.The FT promoter possesses several transcriptional regulatory"blocks,"highly conserved regions among Brassicaceae plants.Different transcription factors bind to specific blocks and affect FT expression,often causing topological changes in FT chromatin structure,such as the formation of DNA loops.We discuss the current understanding of the regulation of FT expression mainly in Arabidopsis and propose future directions related to this topic.

SPL3/4/5 Integrate Developmental Aging and Photoperiodic Signals into the FT-FD Module in Arabidopsis Flowering

Environmental sensitivity varies across developmental phases in flowering plants. In the juvenile phase, mi- croRNA156 （miR156）-mediated repression of SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE （SPL） transcription factors renders Arabidopsis plants incompetent to floral inductive signals, including long- day （LD） photoperiod. During the vegetative phase transition, which accompanies a reduction of miR156 and a concomitant elevation of its targets, plants acquire reproductive competence such that LD signals promote flowering. However, it remains largely unknown how developmental signals are associated with photoperiodic flowering. Here, we show that SPL3, SPL4, and SPL5 （SPL3/4/5） potentiate the FLOWERING LOCUS T （FT）-FD module in photoperiodic flowering. SPL3/4/5 function as transcriptional activators through the interaction with FD, a basic leucine zipper transcription factor which plays a critical role in photoperiodic flowering. SPL3/4/5 can directly bind to the promoters of APETALA1, LEAFY, and FRUITFULL, thus mediating their activation by the FT-FD complex. Our findings demonstrate that SPL3/ 4/5 act synergistically with the FT-FD module to induce flowering under LDs, providing a long-sought mo- lecular knob that links developmental aging and photoperiodic flowering.

Molecular mechanisms for the photoperiodic regulation of flowering in soybean

Photoperiodic flowering is one of the most important factors affecting regional adaptation and yield in soybean(Glycine max). Plant adaptation to long-day conditions at higher latitudes requires early flowering and a reduction or loss of photoperiod sensitivity;adaptation to short-day conditions at lower latitudes involves delayed flowering, which prolongs vegetative growth for maximum yield potential. Due to the influence of numerous major loci and quantitative trait loci(QTLs), soybean has broad adaptability across latitudes. Forward genetic approaches have uncovered the molecular basis for several of these major maturity genes and QTLs. Moreover, the molecular characterization of orthologs of Arabidopsis thaliana flowering genes has enriched our understanding of the photoperiodic flowering pathway in soybean. Building on early insights into the importance of the photoreceptor phytochrome A, several circadian clock components have been integrated into the genetic network controlling flowering in soybean: E1, a repressor of FLOWERING LOCUS T orthologs, plays a central role in this network. Here, we provide an overview of recent progress in elucidating photoperiodic flowering in soybean, how it contributes to our fundamental understanding of flowering time control, and how this information could be used for molecular design and breeding of high-yielding soybean cultivars.

Natural variation and artificial selection of photoperiodic flowering genes and their applications in crop adaptation

Flowering links vegetative growth and reproductive growth and involves the coordination of local environmental cues and plant genetic information.Appropriate timing of floral initiation and maturation in both wild and cultivated plants is important to their fitness and productivity in a given growth environment.The domestication of plants into crops,and later crop expansion and improvement,has often involved selection for early flowering.In this review,we analyze the basic rules for photoperiodic adaptation in several economically important and/or well-researched crop species.The ancestors of rice(Oryza sativa),maize(Zea mays),soybean(Glycine max),and tomato(Solanum lycopersicum)are short-day plants whose photosensitivity was reduced or lost during domestication and expansion to high-latitude areas.Wheat(Triticum aestivum)and barley(Hordeum vulgare)are long-day crops whose photosensitivity is influenced by both latitude and vernalization type.Here,we summarize recent studies about where these crops were domesticated,how they adapted to photoperiodic conditions as their growing area expanded from domestication locations to modern cultivating regions,and how allelic variants of photoperiodic flowering genes were selected during this process.A deeper understanding of photoperiodic flowering in each crop will enable better molecular design and breeding of high-yielding cultivars suited to particular local environments.

Photoperiodic diapause in a subtropical population of Aedes albopictus in Guangzhou,China:optimized fieldlaboratory-based study and statistical models for comprehensive characterization

Background:Aedes albopictus is among the 100 most invasive species worldwide and poses a major risk to public health.Photoperiodic diapause provides a crucial ecological basis for the adaptation of this species to adverse environments.Ae.albopictus is the vital vector transmitting dengue virus in Guangzhou,but its diapause activities herein remain obscure.Methods:In the laboratory,yeast powder and food slurry were compared for a proper diapause determination method,and the critical photoperiod(CPP)was tested at illumination times of 11,11.5,12,12.5,13,and 13.5 h.A 4-parameter logistic(4PL)regression model was selected to estimate the CPP.In the field,the seasonal dynamics of the Ae.albopictus population,egg diapause,and hatching of overwintering eggs were investigated monthly,weekly,and daily,respectively.A distributed lag non-linear model(DLNM)was used to assess the associations of diapause with meteorological factors.Results:In the laboratory,both the wild population and the Foshan strain of Ae.albopictus were induced to diapause at an incidence greater than 80%,and no significant difference(P>0.1)was observed between the two methods for identifying diapause.The CPP of this population was estimated to be 12.312 h of light.In the field,all of the indexes of the wild population were at the lowest levels from December to February,and the Route Index was the first to increase in March.Diapause incidence displayed pronounced seasonal dynamics.It was estimated that the day lengths of 12.111 h at week2016,43 and 12.373 h at week2017,41 contributed to diapause in 50%of the eggs.Day length was estimated to be the main meteorological factor related to diapause.Conclusions:Photoperiodic diapause of Ae.albopictus in Guangzhou of China was confirmed and comprehensively elucidated in both the laboratory and the field.Diapause eggs are the main form for overwintering and begin to hatch in large quantities in March in Guangzhou.Furthermore,this study also established an optimized investigation system and statistical models for the study of Ae.albopictus diapause.These findings will contribute to the prevention and control of Ae.albopictus and mosquito-borne diseases.

Timing of Photoperiodic Flowering：Light Perception and Circadian Clock

Flowering symbolizes the transition of s plant from vegetative phase to reproductive phase and is controlled by fairly complex and highly coordinated regulatory pathways. Over the last decade, genetic studies in Arabidopsis have aided the discovery of many signaling components involved in these pathways. In this review, we discuss how the timing of flowering is regulated by photoperiod and the involvement of light perception and the circadian clock in this process. The specific regulatory mechanisms on CONSTANS expression and CONSTANS stability by the circadian clock and photoreceptors are described in detail. In addition, the roles of CONSTANS, FLOWERING LOCUS T, and several other light signaling and circadian-dependent components in photoperiodic flowering are also highlighted.

Apparent dissociation of photoperiodic time measurement between vernal migration and breeding under dim green light conditions in Gambel＇s white-crowned sparrow Zonotrichia leucophrys gambelii

In seasonally breeding birds, the annual cycle of photoperiod is a principal environmental cue for temporal arrange- ment of different life-history stages, such as migration and breeding. In the past, most research has focused on the mechanisms of photoperiodic control of breeding with less attention paid to migration. In Gambel＇s white-crowned sparrow Zonotrichia leuco- phrys gambelii （GWCS）, photoreceptors for induction of breeding are known to reside in the basal hypothalamus. However, it is unknown whether the sites of photoperiodic reception for vernal migration are the same as those for breeding. Therefore, we hy- pothesized that they may be controlled separately. In this study, we exposed photosensitive GWCSs to low-penetration green light （wavelength at 510 nm） under a regime of 1 lux during the day and 〈0.1 lux at night, and switched the photoperiodic conditions from short day （10 h daytime） to long day （18 h daytime）. The results showed that the experimental birds developed traits associ- ated with vernal migration including mass increase, fat deposition and migratory restlessness behavior when transferred from short day to long day green light cycles, while control birds maintained continuously on short day green light conditions did not ex- press any migration related characteristics. Neither experimental nor control groups showed gonadal recrudescence trader either green light cycles. In support of our hypothesis, we were able to apparently dissociate the photoperiodic responses regulating vernal migra- tion and breeding, which suggests separate mechanisms of photoperiodic time measurement. Such distinct photoperiodic mechanisms may drive the free-tuned temporal arrangement of the two life history stages.

Photoperiod Mediates the Effects of Temperature and Light Intensity on the Proliferation of Ulva prolifera

In order to study the complex effects of photoperiod,temperature,and light intensity on the spore maturation and release number of Ulva prolifera,we cultured thalli segment(2–3 mm)under three different photoperiods(L:D=12:12,14:10 and 10:14),temperature(15℃(LT),25℃(MT)and 30℃(HT))and light intensity(100,200 and 400μmol m^(−2)s^(−1),noted as LL,ML and HL,respectively)conditions.Then the maturation time,spore release number and chlorophyll fluorescence were analyzed.The results suggested that:1)The spore maturation time was accelerated by higher temperature or higher light intensity from 62 h to 36 h,and changes in day length accelerated the spore maturation to a certain extent as compared with 12:12 light/dark cycle;2)Higher light intensity significantly decreased the chlorophyll fluorescence(Fv′/Fm′,NPQ,rETRmax andα)of the mature reproductive segment under 30℃with 12:12 light/dark cycle.But when in the other photoperiods(10:14 and 14:10 conditions),the inhibitory effects of high light intensity were alleviated significantly;3)The optimum condition for the spore maturation and release was 12:12 light/dark cycle,25℃,400μmol m^(−2)s^(−1),with both shorter and longer photoperiod reducing the spore release number;4)Higher light intensity significantly increased the spore release number under 25℃,but these effects were alleviated by 30℃treatment.This study is the first attempt to elucidate the coincidence effects of photoperiod,temperature and light intensity on the reproduction of Ulva,which would help to reveal the mechanism of the rapid proliferation of green tide.

Flowering-time regulation by the circadian clock:From Arabidopsis to crops

Precise timing of flowering in plants is critical for their growth and reproductive processes.One factor controlling flowering time is the cycle of light and darkness within a day,known as the photoperiod.Plants are classified into long-day,short-day,and day-neutral plants based on light requirements for floral initiation.Although the molecular mechanisms that govern this differentiation remain incompletely understood,studies have consistently shown that the circadian clock plays a central role in regulating photoperiod response across diverse plant species.However,there is a scarcity of reviews describing the regulatory network linking the circadian clock with photoperiodic flowering.This review summarizes that regulatory network,focusing on the distinct roles of clock genes in long-day and short-day plants.We also discuss the strategies of clock gene mutations contributing to geographic variation in longday and short-day crops.

Molecular mechanism of flowering time regulation in Brassica rapa:similarities and differences with Arabidopsis

Properly regulated flowering time is pivotal for successful plant reproduction.The floral transition from vegetative growth to reproductive growth is regulated by a complex gene regulatory network that integrates environmental signals and internal conditions to ensure that flowering takes place under favorable conditions.Brassica rapa is a diploid Cruciferae species that includes several varieties that are cultivated as vegetable or oil crops.Flowering time is one of the most important agricultural traits of B.rapa crops because of its influence on yield and quality.The transition to flowering in B.rapa is regulated by several environmental and developmental cues,which are perceived by several signaling pathways,including the vernalization pathway,the autonomous pathway,the circadian clock,the thermosensory pathway,and gibberellin(GA)signaling.These signals are integrated to control the expression of floral integrators BrFTs and BrSOC1s to regulate flowering.In this review,we summarized current research advances on the molecular mechanisms that govern flowering time regulation in B.rapa and compare this to what is known in Arabidopsis.

Effects of heat stress and long photoperiod on the prostate of rats

Objective:To examine light and heat effects on the morphological,histological,and micrometric structure of the prostate of rats.Methods:Thirty adult male rats were divided into three groups.The control group was kept under 20℃-22℃ and an artificial 12 h/12 h day/night cycle;the temperature group was under normal light and at(42±1)℃ heat for 4 to 5 h daily,and the light group was exposed to 8 h/16 h day/night cycle with 20℃-22℃.Rats were weighed five times(at the beginning of the study and every seven days).Five milliliters(mL)of their peripheral blood were taken.The tissue staining was performed using the hematoxylin-eosin(H&E)stain and periodic acid-Schiff(PAS).In the following,tissue and cellular reactions to the PAS were examined.Results:Folds were located entirely on the surface of the anterior lobe and periphery of the other lobes.The secretory units in the anterior lobe were more than the lateral lobe.A strong reaction of the secretory cells to the PAS was observed.Testosterone serum levels of the light group also significantly increased compared to the control group(P<0.05).The most histometric changes of the lobes were established in the lateral lobes.Heat stress resulted in a significant decrease in testosterone levels and transformed prostate tissue.The epithelium and parenchyma to scaffold ratio in the temperature group decreased.Conclusions:Maximum and minimum changes in the ventral lobe happened under the ascent of temperature and light,respectively.The ventral lobe in the study of prostatic hyperplasia should be more considered.

FLOWERING LOCUS T(FT)in Photosensitive Type Chrysanthemum Accelerates Flowering in Arabidopsis

FLOWERING LOCUS T(FT)is an important factor for integrating flowering signals through the photoperiod pathway,which significantly promotes flowering.Most chrysanthemum varieties are short-day plants,sensitive to the photoperiod,which limits their ornamental and annual production supply.In this study,we aim to analyze the nutrients and flowering-related genes of chrysanthemums with different photoperiod types and to clone and verify the function of the flowering-related gene CmFT.We found that the formation of floral buds requires the accumulation of starch while consuming soluble sugars and the expression patterns of flowering-related genes GIGANTEA(GI),CONSTANS(CO),and FT in C.morifolium‘Zilian’and C.morifolium‘Zihongtuogui’had a certain synchronization during floral buds differentiation according to our quantitative validation,and the expression levels of CmGI,CmCO and CmFT in C.morifolium‘Zihongtuogui’were higher than those in C.morifolium.‘Zilian’in the later stage of differentiation.CmFT was cloned from photosensitive chrysanthemums-C.morifolium‘Zihongtuogui’and polypeptide alignment and phylogenetic analysis showed that CmFT was clustered in FT-like subfamily.In further functional verification,we obtained two Arabidopsis transgenic lines.Our results showed that CmFT transgenic ft mutant lines can significantly accelerate flowering in Arabidopsis.Thus,we can initially confirm that CmFT plays an important role in promoting flowering,which may be the key reason for the photosensitivity of C.morifolium‘Zihongtuogui’.Overall,the results of this study are of great importance in revealing the flowering mechanism of different photoperiod types of chrysanthemums.

Common Organic Amendment (Rice Straw) Can Reduce Salinity Effects on Bean (Phaseolus vulgaris) Growth with or without Photoperiod Manipulation

Soil salinity is a major limiting factor for crop production in coastal areas of Bangladesh. Cheap and sustainable management of soil salinity is hence most sought out topics in agricultural research. Conceptualizing that idea in mind, a pot experiment was conducted in the Department of Soil, Water & Environment, University of Dhaka in order to analyze if common organic amendments (rice straw, saw dust) coupled with reduce photoperiod can mitigate salinity effect on the growth of bean (Phaseolus vulgaris). The experiment was set up following completely randomized design (CRD) with nine treatments and three replications containing Tc (Control), T1 (Ambient photoperiod + 110 mM Salinity treatment + Rice straw), T2 (Reduced photoperiod + 110 mM Salinity treatment + Rice straw), T3 (Ambient photoperiod + 220 mM Salinity treatment + Rice straw), T4 (Reduced photoperiod + 220 mM Salinity treatment + Rice straw), T5 (Ambient photoperiod + 110 mM Salinity treatment + Saw dust), T6 (Reduced photoperiod + 110 mM Salinity treatment + Saw dust), T7 (Ambient photoperiod + 220 mM Salinity treatment + Saw dust) and T8 (Reduced photoperiod + 220 mM Salinity treatment + Saw dust). Organic amendments were used separately at the rate of 12 ton/ha. The highest plant height (98.67 cm), root length (12.5 cm), pod number (10.33), leaf area (13.99 cm2), fresh weight (680 kg/ha), dry weight (316.67 kg/ha) were recorded with the treatment T1 while the second-best treatment was treatment T2 (with highest harvest index 0.040) and these results were statistically significant (p < 0.001). In post-harvest soil, pH, EC, OC, OM;available N, P, K, S;total Ca, Mg, Zn, Mn were increased significantly in treatment T1. The overall results illustrated that the best growth and yield performances were achieved in the treatment T1 and T2.

Effect of Shortening Day Length on Immune Function in Siberian Hamsters

In order to understand the effect of gradual changes in photoperiod on immune function, adult female Siberian hamsters (Phodopus sungorus) were randomly divided into the control group (12L:12D, Con, n = 11) and the shortening day length group (SD, n = 11), in which day length was reduced from 12:12 h to 8:16 h light-dark cycle at the pace of half an hour every week. Meanwhile the winter immunoenhancement hypothesis, which holds that animals’ immune function would be enhanced in winter or winter-like conditions, was tested. Gradual shortening day length had no effect on body mass and body composition including wet carcass mass, the subcutaneous, retroperitoneal, mesenteric and total body fat masses in Siberian hamsters. The masses of liver and small intestine with contents were higher in the SD group than in the Con group, however other organ masses such as brain, heart, kidney and so on did not differ between the two groups. Phytohemagglutinin (PHA) response after 24 h of PHA injection was enhanced by the shortening photoperiod, which supported the winter immunoenhancement hypothesis. The masses of spleen and thymus, white blood cells, bacteria killing capacity indicative of innate immunity were not affected, which did not support this hypothesis. In summary, gradually decrease in day length increased cellular immunity, but had no effect on other immunological parameters in Siberian hamsters.

SPECIFIC PROTEIN OCCURRENCE RELATED WITH PHOTOPERIODIC FLOWER INDUCTION IN THE COTYLEDONS OF Pharbitis nil CV. VIOLET

In our experiment, three groups of seedlings of SDP Pharbitis nil cv. violet were sepa-rately treated with three different photoperiods (1,16 h dark period--SD; 2, continuous illumi-nation--CL; 3, 16 h dark treatment with 10 min white light in the middle of the dark period--NB). By analysing proteins in the cotyledons from three groups with 2-D PAGE, we found nodifference in protein pattern between the three groups at 0 or 8 h after photoperiodic treatments.At 24 h after the treatments, a specific protein(MW:19 kD; pI: 4.5)appeared only in the cotyledonsof the seedlings which endured SD. This protein disappeared at 72 h after SD. ActinomycinD could inhibit flowering and the specific protein occurrence when applied to cotyledonsprior to SD, but it had no inhibition effect on flowering as well as the specific proteinoccurrence when applied to cotyledons after SD. Chloroamphenicol, a protein synthesisinhibitor, inhibited flowering when applied to cotyledons prior to or immediately after SD,but it did not inhibit flowering when applied to cotyledons at 24 h after SD. With the jointconsideration of the effects of defoliation and inhibitor applications on flowering, wededuced that the 19 kD protein occurrence correlated with the commitment to flowering. Thegene transcription related with induction was fulfilled within the SD period, while thespecific protein synthesis lasted 24 h after SD. The key regulation step of biochemical changesduring induction was at the transcriptional level.

Geographic variation in photoperiodic diapause induction and diapause intensity in Sericinus montelus （Lepidoptera Papilionidae）

Due to the risk of extinction and ornamental value of the swallowtail butterfly, Sericinus montelus Gray （Lepidoptera： Papilionidae） in China, knowledge about local adaptations is important for the conservation and economical utilization of the species. In the present study, photoperiodie diapause induction and diapause intensity of S. montelus populations from Jiamusi （46°37＇N）, Beijing （40° 15＇N）, Zibo （36°48＇N）, Fangxian （32°36＇N）, Wuhan （30°33＇N） and Huaihua （27°33＇N） were characterized at 25℃. Logistic regression analysis revealed a significant population x hours of light interaction, confirming that photoperiodic responses varied among populations. The critical photoperiod was positively correlated with latitude and increased toward the north at a rate of about 1 h for each 6.67 degrees of latitude. Survival analyses indicated that survival time of diapausing pupae before adult eclosion differed significantly among populations at 25℃ and 16 ： 8 L ＂D h. The mean duration of pupal diapause was also positively correlated with latitude. Our study reveals geographic variation in the critical photoperiod for diapause induction and in diapause intensity of S. montelus. These results provide useful information for our general understanding about seasonal adaptation in insects and may also be used to predict how geographic populations respond to climate warming.

Identification of Soybean Genes Involved in Circadian Clock Mechanism and Photoperiodic Control of Flowering Time by In Silico Analyses

Glycine max is a photoperiodic short-day plant and the practical consequence of the response is latitude and sowing period limitations to commercial crops. Genetic and physiological studies using the model plants Arabidopsis thaliana and rice （Oryza sativa） have uncovered several genes and genetic pathways controlling the process, however information about the corresponding pathways in legumes is scarce. Data mining prediction methodologies, including multiple sequence alignment, phylogeneUc analysis, bioinformaUcs expression and sequence motif pattern identification, were used to identify soybean genes involved in day length perception and photoperiodic flowering induction. We have investigated approximately 330 000 sequences from open-access databases and have identified all bona fide central oscillator genes and circadian photoreceptors from A. thaliana in soybean sequence databases. We propose a working model for the photoperiodic control of flowering time in G. max, based on the identified key components. These results demonstrate the power of comparative genomics between model systems and crop species to elucidate the several aspects of plant physiology and metabolism.