Identification and Fine Mapping of a Gene Related to Pale Green Leaf Phenotype near the Centromere Region in Rice(Oryza sativa)

A thermo-insensitive pale green leaf mutant （pgl2） was isolated from T-DNA inserted transgenic lines of rice （Oryza sativa L. subsp, japonica cv. Nipponbare）. Genetic analysis indicated that the phenotype was caused by a recessive mutation in a single nuclear-encoded gene. To map the PGL2gene, an F2 population was constructed by crossing the mutant with Longtefu （Oryza sativa L. subsp, indica）. The PGL2 locus was roughly linked to SSR marker RM331 on chromosome 8. To finely map the gene, 14 new InDel markers were developed around the marker, and PGL2 was further mapped to a 2.37 Mb centromeric region. Analysis on chlorophyll contents of leaves showed that there was no obvious difference between the mutant and the wild type in total chlorophyll （Chl） content, while the ratio of Chl a / Chl b in the mutant was only about 1, which was distinctly lower than that in the wild type, suggesting that the PGL2 gene was related to the conversion between Chl a and Chl b. Moreover, the method of primer design around the centromeric region was discussed, which would provide insight into fine mapping of the functional genes in plant centromeres.

Site-Specific Nitrogen Management in Dry Direct-Seeded Rice Using Chlorophyll Meter and Leaf Colour Chart

The need to maintain high rice yields and improve fertilizer nitrogen(N)-use efficiency has fueled the use of tools such as leaf colour chart(LCC) and chlorophyll meter(SPAD meter) in managing fertilizer N based on colour of the leaf. Field experiments were conducted during 2011 to 2013 at Ludhiana, India to assess the need for basal N application and to establish critical threshold values of leaf greenness as measured by LCC and SPAD meter for formulating strategies for in-season management of fertilizer N in dry direct-seeded rice(DDSR). Avoiding application of N at sowing did not adversely affect rice grain yield, indicating that basal N application in DDSR was not necessary and might lead to reduced N-use efficiency. Monitoring N uptake rate during the growing season of DDSR suggested that N uptake rate peaked at the two growth stages: maximum tillering(42 to 56 days after sowing(DAS))and panicle initiation stages(70 to 84 DAS). Using the Cate-Nelson procedure, critical LCC and SPAD meter values for fertilizer N application worked out to be 4 and 37, respectively. Real-time fertilizer N management strategy based on applying 30 kg N ha-1whenever SPAD meter or LCC readings fell below the critical values maintained optimum rice yields along with higher N-use efficiency than that observed by following blanket recommendation for fertilizer N in the region. The fixed-time variable-dose strategy consisted of applying prescriptive doses of 20 kg N ha-1at 14 DAS and 30 kg N ha-1at 28 DAS and corrective doses of 30, 40 or 50 kg N ha-1at 49 and 70 DAS depending upon LCC shade to be ≥ 4, 4–3.5, or < 3.5 and SPAD meter readings to be ≥ 40, 40–35, or< 35, respectively. This strategy also resulted in optimal rice yield along with higher N-use efficiency as compared to the blanket recommendation. This study revealed that in DDSR, fertilizer N could be managed more efficiently using the tools of LCC and SPAD meter than the current blanket recommendation.

Behavioral responses for evaluating the attractiveness of specific tea shoot volatiles to the tea green leafhopper, Empoaca vitis

The tea green leafhopper, Empoasca vitis Gothe, is one of the most serious insect pests of tea plantations in China's Mainland. Over the past decades, this pest has been controlled mainly by spraying pesticides. Insecticide applications not only have become less effective in controlling damage, but even more seriously, have caused high levels of toxic residues in teas, which ultimately threatens human health. Therefore, we should seek a safer biological control approach. In the present study, key components of tea shoot volatiles were identified and behaviorally tested as potential leafhopper attractants. The following 13 volatile compounds were identified from aeration samples of tea shoots using gas chromatography-mass spectrometry （GC-MS）： （E）-2-hexenal, （Z）-3-hexen-1- ol, （Z）-3-hexenyl acetate, 2-ethyl-1-hexanol, （E）-ocimene, linalool, nonanol, （Z）-butanoic acid, 3-hexenyl ester, decanal, tetradecane, β-caryophyllene, geraniol and hexadecane. In Y-tube olfactometer tests, the following individual compounds were identified： （E）-2- hexenal, （E）-ocimene, （Z）-3-hexenyl acetate and linalool, as well as two synthetic mixtures （called blend 1 and blend 2） elicited significant taxis, with blend 2 being the most attractive. Blend 1 included linalool, （Z）-3-hexen-l-ol and （E）-2-hexenal at a 1： 1：1 ratio, whereas blend 2 was a mixture of eight compounds at the same loading ratio： （E）-2-hexenal, （Z）- 3-hexen-l-ol, （Z）-3-hexenyl acetate, 2-penten-l-ol, （E）-2-pentenal, pentanol, hexanol and 1-penten-3-ol. In tea fields, the bud-green sticky board traps baited with blend 2, （E）-2- hexenal or hexane captured adults and nymphs of the leafhoppers, with blend 2 being the most attractive, foUowed by （E）-2-hexenal and hexane. Placing sticky traps baited with blend 2 or （E）-2-hexenal in the tea fields significantly reduced leathopper populations. Our results indicate that the bud-green sticky traps baited with tea shoot volatiles can provide a new tool for monitoring and managing the tea leafhopper.

Identification of a delayed leaf greening gene from a mutation of pummelo

Delayed greening of young leaves is an unusual phenomenon of plants in nature.Citrus are mostly evergreen tree species.Here,a natural mutant of“Guanxi”pummelo(Citrus maxima),which shows yellow leaves at the young stage,was characterized to identify the genes underlying the trait of delayed leaf greening in plants.A segregating population with this mutant as the seed parent and a normal genotype as the pollen parent was generated.Two DNA pools respectively from the leaves of segregating seedlings with extreme phenotypes of normal leaf greening and delayed leaf greening were collected for sequencing.Bulked segregant analysis(BSA)and In Del marker analysis demonstrated that the delayed leaf greening trait is governed by a 0.3 Mb candidate region on chromosome 6.Gene expression analysis further identified a key candidate gene(Citrus Delayed Greening gene 1,CDG1)in the 0.3 Mb region,which showed significantly differential expression between the genotypes with delayed and normal leaf greening phenotypes.There was a 67 bp In Del region difference in the CDG1 promoter and the In Del region contains a TATA-box element.Confocal laser-scanning microscopy revealed that the CDG1-GFP fusion protein signals were co-localized with the chloroplast signals in the protoplasts.Overexpression of CDG1 in tobacco and Arabidopsis led to the phenotype of delayed leaf greening.These results suggest that the CDG1 gene is involved in controlling the delayed leaf greening phenotype with important functions in chloroplast development.

Correction of leaf nutrient resorption efficiency on the mass basis

Nutrient resorption is a crucial mechanism for plant nutrient conservation,but most previous studies did not consider the leaf-mass loss during senescence due to lack of measured data.This would lead to an underestimation of nutrient resorption efficiency(NuRE),or calculating NuRE of various species based on the average mass loss at plant-functional-group level in the literature,thus affecting its accuracy.Here we measured the leaf-mass loss to correct NuRE with the species-specific mass loss correction factor(MLCF),so as to foster a more accurate calculation of the nutrient fluxes within and between plants and the soil.Green leaves and senesced leaves were collected from 35 dominant woody plants in northern China.Mass of green and senesced leaves were measured to calculate the MLCF at species level.The MLCF was reported for each of the 35 dominant woody plants in northern China.These species averagely lost 17%of the green-leaf mass during leaf senescence,but varied greatly from 1.3%to 36.8%mass loss across the 35 species,or 11.7%to 19.6%loss across the functional types.Accordingly,the MLCF varied from 0.632 to 0.987 across the 35 species with an average value 0.832.The NuRE corrected with MLCF was remarkably increased on the whole(e.g.both the average nitrogen and phosphorus NuRE became about 9%higher,or more accurate),compared with the uncorrected ones,especially in the case of low resorption efficiencies.Our field data provide reliable references for the MLCF of plants in related regions at both species and functional-type levels,and are expected to promote more accurate calculations of NuRE.

A Green Leaf on the Big Tree

"WITH a dyed darkish-blue apron" was myself portrait when I first entered literarycircles. My hometown Chumen in Yuhuan is asmall town by the sea, a land of fish and ricein the southern reaches of the ChangjiangRiver. The gong and drum for the Liberationsounded in my childhood. I was infatuated bybooks then; the wing of ideas often entered mydreams like beautiful butterflies.

Mapping Quantitative Trait Loci for Post-Anthesis Dry Matter Accumulation in Wheat

Post-anthesis photoassimilation is very important for wheat （Triticum aestivum L.） grain filling. The aim of the present study was to map quantitative trait loci （QTL） for post-anthesis dry matter accumulation （DMA）. A set of 120 doubled haploid （DH） lines, derived from winter wheat varieties Hanxuan 10 and Lumai 14, was grown under field conditions in two consecutive growing seasons during 2002-2004 in Beijing. Post-anthesis DMA per culm and related traits, including flag leaf greenness （FLG） and flag leaf weight （FLW; dry weight per flag leaf） at flowering, and grain weight per ear （GWE） were investigated. All traits segregated continuously in the DH population in both trials. The DMA was significantly and positively correlated with GWE, with the correlation coefficients being 0.79 and 0.66 in the 2002-2003 and 2003-2004 growing seasons （both P〈0.01）, suggesting the importance of DMA in grain filling. Further correlation analysis showed that FLW was more closely correlated with DMA and GWE than FLG in both growing seasons, indicating that FLW was more important than FLG in influencing DMA and GWE. In total, 30 QTLs for these four traits were mapped and distributed on 10 chromosomes. Phenotypic variations explained by an individual QTL were in the range 5.8%-21.3%, 5.9%-17.2%, 5.1%-18.1%, and 5.6%-16.2% for FLG, FLW, DMA, and GWE, respectively. Eight QTLs for DMA were detected, of which four （on chromosome arms 2AS, 4BL, 5AS, and 7AS） were linked with QTLs for GWE; two （on chromosome arms 5BL and 7BL） coincided with QTLs for FLW. These results may provide useful information for developing marker-assisted selection for the improvement of DMA.

Language of plants: Where is the word?

Plants emit biogenic volatile organic compounds（BVOCs） causing transcriptomic, metabolomic and behavioral responses in receiver organisms. Volatiles involved in such responses are often called ＂plant language＂. Arthropods having sensitive chemoreceptors can recognize language released by plants. Insect herbivores, pollinators and natural enemies respond to composition of volatiles from plants with specialized receptors responding to different types of compounds. In contrast, the mechanism of how plants＂hear＂ volatiles has remained obscured. In a plant-plant communication, several individually emitted compounds are known to prime defense response in receiver plants with a specific manner according to the chemical structure of each volatile compound. Further, composition and ratio of volatile compounds in the plant-released plume is important in plantinsect and plant-plant interactions mediated by plant volatiles. Studies on volatile-mediated plant-plant signaling indicate that the signaling distances are rather short, usually not longer than one meter. Volatile communication from plants to insects such as pollinators could be across distances of hundreds of meters. As many of the herbivore induced VOCs have rather short atmospheric life times, we suggest that in long-distant communications with plant volatiles,reaction products in the original emitted compounds may have additional information value of the distance to emission source together with the original plant-emitted compounds.

Nutrient resorption and stoichiometric responses of poplar(Populus deltoids)plantations to N addition in a coastal region of eastern China

Aims Leaf nutrient resorption is sensitive to changes in soil nutrients.However,the effects of N deposition on nutrient resorption efficiency(NuRE)in plant macro-nutrients remain unclear.Poplar(Populus deltoids)is one of the most extensively cultivated hardwood species worldwide.We explored general patterns and dominant drivers of NuRE and stoichiometry of poplar plantations in response to N addition.Methods We conducted a 4-year N-addition experiment to explore NuRE and stoichiometric responses to N addition in two poplar(P.deltoids)plantations(8-and 12-year-old stands)in a coastal region of eastern China.We measured soil and foliar(green and senesced leaves)concentrations of nitrogen(N),phosphorus(P),potassium(K),calcium(Ca)and magnesium(Mg)for a series of N addition treatments including N_(0)(0 kg N ha^(−1)yr^(−1)),N_(1)(50 kg N ha^(−1)yr^(−1)),N_(2)(100 kg N ha^(−1)yr^(−1)),N_(3)(150 kg N ha^(−1)yr^(−1))and N_(4)(300 kg N ha^(−1)yr^(−1)).Important Findings Consistent for(both)8-and 12-year-old stands,N addition did not affect the NuRE and stoichiometry(with the exception of CaRE and CaRE:MgRE ratio).N resorption efficiency–P resorption efficiency(NRE–PRE)scaling slopes were consistently less than 1.0 under N addition.These results suggest that NRE generally decouples from PRE within each N treatment.Moreover,these results point to robust control of green leaf nutritional status on nutrient resorption processes as indicated by the positive relationships between NuRE and green leaf nutrient concentrations.Our findings provided a direct evidence that growth in 12-year-old poplar plantations was N-limited in the coastal region of eastern China.

An oriental melon 9-lipoxygenase gene CmLOX09 response to stresses, hormones, and signal substances

In plants, lipoxygenases （LOXs） play a crucial role in biotic and abiotic stresses. In our previous study, five 13-LOX genes of oriental melon were regulated by abiotic stress but it is unclear whether the 9-LOX is involved in biotic and abiotic stresses. The promoter analysis revealed that CmLOX09 （type of 9-LOX） has hormone elements, signal substances, and stress elements. We analyzed the expression of CmLOX09 and its downstream genes--CmHPL and CmAOS-in the leaves of four-leaf stage seedlings of the oriental melon cultivar ＂Yumeiren＂ under wound, hormone, and signal substances. CmLOX09, CmHPL, and CmAOS were all induced by wounding. CmLOX09 was induced by auxin （indole acetic acid, IAA） and gibberellins （GA3）; however, CrnHPL and CmAOS showed differential responses to IAA and GA3. CmLOX09, CmHPL, and CmAOS were all induced by hydrogen peroxide （H2O2） and methyl jasmonate （MeJA）, while being inhibited by abscisic acid （ABA） and salicylic acid （SA）. CmLOX09, CmHPL, and CmAOS were all induced by the powdery mildew pathogen Podosphaera xanthii. The content of 2-hexynol and 2-hexenal in leaves after MeJA treatment was significantly higher than that in the control. After infection with P. xanthii, the diseased leaves of the oriental melon were divided into four levels-levels 1,2, 3, and 4. The content of jasmonic acid （JA） in the leaves of levels 1 and 3 was significantly higher than that in the level 0 leaves. In summary, the results suggested that CmLOX09 might play a positive role in the response to MeJA through the hydroperoxide lyase （HPL） pathway to produce C6 alcohols and aldehydes, and in the response to P. xanthiithrough the allene oxide synthase （AOS） pathway to form JA.

Comparison of pretreatment,preservation and determination methods for foliar pH of plant samples

To compare current methods of pretreatment/determination for plant foliar pH,we proposed a method for longperiod sample preservation with little interference with the stability of foliar pH.Four hundred leaf samples from 20 species were collected and four methods of pH determination were used:refrigerated(stored at 4°C for 4 days),frozen(stored at−16°C for 4 days),oven-dried and fresh green-leaf pH(control).To explore the effects of different leaf:water mixing ratio on the pH determination results,we measured oven-dried green-leaf pH by leaf:water volume ratio of 1:8 and mass ratio of 1:10,and measured frozen senesced-leaf pH by mass ratio of 1:10 and 1:15.The standard major axis regression was used to analyze the relationship and the conversion equation between the measured pH with different methods.Foliar pH of refrigerated and frozen green leaves did not signifcantly differ from that of fresh green-leaf,but drying always overrated fresh green-leaf pH.During the feld sampling,cryopreservation with a portable refrigerator was an advisable choice to get a precise pH.For long-duration feld sampling,freezing was the optimal choice,and refrigeration is the best choice for the shorttime preservation.The different leaf:water mixing ratio signifcantly infuenced the measured foliar pH.High dilution reduced the proton concentration and increased the measured pH.Our fndings provide the conversion relationships between the existing pretreatment and measurement methods,and establish a connection among pH determined by different methods.Our study can facilitate foliar pH measurement,thus contributing to understanding of this interesting plant functional trait.