Circadian rhythms in the growth and reproduction of the brown alga Undaria pinnatifida and gametogenesis under different photoperiods

Circadian growth rhythm of the juvenile sporophyte of the brown alga Undaria pinnatifida was measured with the computer-aided image analysis system in constant florescent white light under constant temperature （ 10 ℃ ）. The growth rhythm persisted for 4 d in constant light with a free-running period of 25.6 h. Egg release from filamentous gametophytes pre-cultured in the light - dark regime was evaluated for six consecutive days at fixed time intervals in constant white light and 12 h light per day. Egg release rhythm persisted for 3 d in both regimes, indicating the endogenous nature. Temporal scale of egg release and gametogenesis in 18, 16, 12 and 8 h light per day were evaluated respectively using vegetatively propagated filamentous gametophytes. Egg release occurred 2 h after the onset of dark phase and peaked at midnight. Evaluation of the rates of oogonium formation, egg release or fertilization revealed no significant differences in four light-dark regimes, indicating the great plasticity of sexual reproduction. No photoperiodic effect in gametogenesis in terms of oogonium formation and egg release was found, but fertilization in short days was significantly higher than in long days. Results of this investigation further confirmed the general occurrence of circadian rhythms in intertidal seaweed species.

Hypothalamic-Pituitary-Gonadal(HPG)Axis and Transcriptional Regulatory Elements Regulate piwil2 Gene Expression During Gametogenesis and Gonadal Development in Japanese Flounder(Paralichthys olivaceus)

The P-element induced wimpy testis(Piwi)proteins,which are associated with PIWI-interacting RNAs(piRNAs),play important roles in meiosis,germ cell division,and germline maintenance.In this study,we identified and characterized the Paralichthys olivaceus piwil2 gene,a constituent factor of the piRNA pathways involved in the biogenesis of reproductive development.The biological analysis indicated that piwil2,which contains PAZ and PIWI domains,was highly conserved between teleosts and tetrapods.The piwil2 distribution profile in different tissues confirmed a sexually dimorphic expression pattern,with a higher expression level in testis.In situ hybridization demonstrated that piwil2 was expressed in the oogonia and oocytes of the ovaries as well as in the Sertoli cells and spermatocytes of the testes.Gene piwil2 showed a maternally inherited expression pattern during embryonic development,and was highly expressed during the early embryonic development.Different luciferase reporters were constructed to determine the transcriptional regulatory mechanisms of piwil2.The piwil2 core promoter region was located at−360 bp to−60 bp.Furthermore,some representative sex hormones,including human chorionic gonadotropin,17α-methyltestosterone,and estradiol-17βhad distinct regulatory effects on piwil2.In a summery,these results indicate that piwil2,regulated by sex hormones and transcriptional elements,has vital functions in the reproductive cycle and gonadal development.

RebL1 is required for macronuclear structure stability and gametogenesis in Tetrahymena thermophila

Histone modification and nucleosome assembly play important roles in chromatin-related processes.Histone chaperones form different complexes and coordinate histone transportation and assembly.Various histone chaperone complexes have been identified in different organisms.The ciliate protozoa(ciliates)have various chromatin structures and different nuclear morphology.However,histone chaperone components and functions of different subunits remain unclear in ciliates.Tet-rahymema thermophila contains a transcriptionally active macronucleus(MAC)and a transcriptionally inactive micronu-cleus(MIC)which exhibit multiple replication and various chromatin remodeling progresses during vegetative growth and sexual developmental stages.Here,we found histone chaperone RebL1 not only localized evenly in the transcriptionally active MAC but also dynamically changed in the MIC during vegetative growth and sexual developmental stages.REBL1 knockdown inhibited cellular proliferation.The macronuclear morphology became bigger in growing mutants.The abnormal macronuclear structure also occurred in the starvation stage.Furthermore,micronuclear meiosis was disturbed during sexual development,leading to a failure to generate new gametic nuclei.RebL1 potentially interacted with various factors involved in histone-modifying complexes and chromatin remodeling complexes in different developmental stages.REBL1 knockdown affected expression levels of the genes involved in chromatin organization and transcription.Taken together,RebL1 plays a vital role in maintaining macronuclear structure stability and gametogenesis in T.thermophila.

Spindle-E is essential for gametogenesis in the silkworm, Bombyx mori

As a defense mechanism against transposable elements,the PIWI-interacting RNA(piRNA)pathway maintains genomic integrity and ensures proper gametogenesis in gonads.Numerous factors are orchestrated to ensure normal operation of the piRNA pathway.Spindle-E(Spn-E)gene was one of the first genes shown to participate in the piRNA pathway.In this study,we performed functional analysis of Spn-E in the model lepidopteran insect,Bombyx mori.Unlike the germline-specific expression pattern observed in Drosophila and mouse,BmSpn-E was ubiquitously expressed in all tissues tested,and it was highly expressed in gonads.Immunofluorescent staining showed that BmSpn-E was localized in both germ cells and somatic cells in ovary and was expressed in spermatocytes in testis.We used a binary transgenic CRISPR/Cas9 system to construct BmSpn-E mutants.Loss of BmSpn-E expression caused derepression of transposons in gonads.We also found that mutant gonads were much smaller than wild-type gonads and that the number of germ cells was considerably lower in mutant gonads.Quantitative real-time PCR analysis and TUNEL staining revealed that apoptosis was greatly enhanced in mutant gonads.Further,we found that the BmSpn-E mutation impacted gonadal development and gametogenesis at the early larval stage.In summary,our data provided the first evidence that BmSpn-E plays vital roles in gonadal development and gametogenesis in B.mori.

Arabidopsis Transcription Factor Genes NF-YA 1, 5, 6, and 9 Play Redundant Roles in Male Gametogenesis, Embryogenesis, and Seed Development

Nuclear factor Y （NF-Y） is a highly conserved transcription factor presented in all eukaryotic organisms, and is a heterotrimer consisting of three subunits： NF-YA, NF-YB, and NF-YC. In Arabidopsis, these three subunits are encoded by multigene families. The best-studied member of the NF-Y transcription factors is LEAFY COTYLEDON1 （LEC1）, a NF-YB family member, which plays a critical role in embryogenesis and seed maturation. However, the function of most NF-Y genes remains elusive. Here, we report the characterization of four genes in the NF-YA family. We found that a gain- of-function mutant of NF-YA1 showed defects in male gametogenesis and embryogenesis. Consistently, overexpression of NF-YA1, 5, 6, and 9 affects male gametogenesis, embryogenesis, seed morphology, and seed germination, with a stronger phenotype when overexpressing NF-YA1 and NF-YA9. Moreover, overexpression of these NF-YA genes also causes hypersensitivity to abscisic acid （ABA） during seed germination, retarded seedling growth, and late flowering at different degrees. Intriguingly, overexpression of NF-YA1, 5, 6, and 9 is sufficient to induce the formation of somatic embryos from the vegetative tissues. However, single or double mutants of these NF-YA genes do not have detectable phenotype. Collectively, these results provide evidence that NF-YA1, 5, 6, and 9 play redundant roles in male gameto- phyte development, embryogenesis, seed development, and post-germinative growth.

The Arabidopsis Anaphase-Promoting Complex/Cyclosome Subunit 1 is Critical for Both Female Gametogenesis and Embryogenesis

Anaphase-promoting complex/cyclosome （APC/C）, a multisubunit E3 ligase, plays a critical role in cell cycle control, but the functional characterization of each subunit has not yet been completed. To investigate the function of APC1 in Arabidopsis, we analyzed four mutant alleles of APC1, and found that mutation in APC1 resulted in significantly reduced plant fertility, accumulation of cyclin B, and disrupted auxin distribution in embryos. The three mutant alleles apcl-1, apcl-2 and apcl-3 shared variable defects in female gametogenesis including degradation, abnormal nuclear number, and disrupted polarity of nuclei in the embryo sac as well as in embryogenesis, in which embryos were arrested at multiple stages. All of these defects are similar to those previously identified in apc4. The mutant apcl-4, in which the T-DNA was inserted after the transmembrane domain at the C-terminus, showed much more severe phenotypes; that is, most of the ovules were arrested at the one-nucleate female gametophyte stage （stage FG1）. In the apcl apc4 double mutants, the fertility was further reduced by one-third in apcl-ll＋ apc4-1/＋, and in some cases no ovules even survived in siliques of apcl-4/＋ apc4-1/＋. Our data thus suggest that APC1, an essential component of APC/C, plays a synergistic role with APC4 both in female gametogenesis and in embryogenesis.

Reconstitution of Gametogenesis In Vitro:Meiosis Is the Biggest Obstacle

Germ-line cells are responsible for transmitting genetic and epigenetic information across generations, and ensuring the creation of new individuals from one generation to the next. Gametogenesis process requires several rigorous steps, including primordial germ cell （PGC） specification, proliferation, migration to the gonadal ridges and differentiation into mature gametes such as sperms and oocytes. But this process is not clearly explored because a small number of PGCs are deeply embedded in the developing embryo. In the attempt to establish an in vitro model for understanding gametogenesis process well, several groups have made considerable progress in differen- tiating embryonic stem cells （ESCs） and adult stem cells （ASCs） into germ-like cells over the past ten years. These stem cell-derived germ cells appear to he capable of undergoing meiosis and generating both male and female gametes. But most of gametes turn out to be not fully functional due to their abnormal meiosis process compared to endogenous germ cells. Therefore, a robust system of differentiating stem cells into germ cells would enable us to investigate the genetic, epigenetic and environmental factors associated with germ cell development. Here, we review the stem cell-derived germ cell development, and discuss the potential and challenges in the differentiation of functional germ cells from stem cells.

SNAIL1 is essential for female gametogenesis in Arabidopsis thaliana

Two yeast Brix family members Ssfl and Ssf2, involved in large ribosomal subunit synthesis, are essential for yeast cell viability and mating efficiency. Their putative homologs exist in the Arabidopsis genome; however, their role in plant development is unknown. Here, we show that Arabidopsis thaliana SNAIL1 （AtSNAIL1）, a protein sharing high sequence identity with yeast Ssfl and Ssf2, is critical to mitosis progression of female gametophyte development. The snail1 homozygous mutant was nonviable and its heterozygous mutant was semi-sterile with shorter siliques. The mutation in SNAIL1 led to absence of female transmission and reduced male transmission. Further phenotypic analysis showed that the synchronic development of female gametophyte in the snail1 heterozygous mutant was greatly impaired and the snaih pollen tube growth, in vivo, was also compromised. Furthermore, SNAIL1 was a nucleolar- localized protein with a putative role in protein synthesis. Our data suggest that SNAIL1 may function in ribosome biogenesis like Ssf1 and Ssf2 and plays an important role during megagametogenesis in Arabidopsis.

Somatostatin 4 regulates growth and modulates gametogenesis in zebrafish

Somatostatin(SST)plays important roles in growth and development.In teleost fishes six SST encoding genes(sst1 to sst6)have been identified although few studies have addressed their function.Here we aim to determine the function of the teleost specific sst4 in the zebrafish.A CRISPR/Cas9 sst4 zebrafish mutant with loss of function(sst4−/−)was produced which grew significantly faster and was heavier at the onset of gonadal maturation than the wild type(WT).Consistent with their faster growth,liver igf1,igf2a and igf2b expression was significantly upregulated in the sst4−/−fish compared to the WT.Histological examination of the ovaries and testis indicated that sst4−/−fish had slightly delayed testicular gametogenesis compared to the WT.Significantly lower expression of igf3,amh,insl3,hsd17b3,hsd11b2,hsd20b,cyp11b and cyp17 was consistently observed in the sst4−/−testis.In contrast,the ovaries had lower expression of igf1,igf2a and cyp19a1a but increased expression of igf2b and hsd20b.The gonadotrophin beta subunits(fshb and lhb)in the brain were downregulated indicating the brain-pituitary-gonadal axis was downregulated in the sst4−/−fish and suggesting that the steroid production is compromised in the maturing gonads.In addition,analysis of sst1 and sst3 mRNA levels in sst4−/−fish suggests a dosage compensation effect of sst1 in the brain and liver.Altogether,the results from the zebrafish sst4−/−line support the idea that sst4 is involved in the regulation of igf signalling,somatic growth and reproduction since steroidogenesis and gametogenesis at pubertal onset were compromised.

ABORTED GAMETOPHYTE 1 is required for gametogenesis in Arabidopsis

In flowering plants, the male and female gameto- genesis is a crucial step of sexual reproduction. Although many genes have been identified as being involved in the gametogenesis process, the genetic mechanisms underlying gametogenesis remains poorly understood. We reported here characterization of the gene, ABORTED GAMETOPHYTE 1 （AOGI） that is newly identified as essential for gametogenesis in Arabidopsis thaliana. AOG1 is expressed predominantly in reproductive tissues including the developing pollen grains and ovules. The AOG1 protein shares no significant amino acid sequence similarity with other documented proteins and is located mainly in nuclei of the cells. Mutation in AOG~ caused degeneration of pollen at the uninucleate microspore stage and severe defect in embryo sacs, leading to a significant reduction in male and female fertility.Furthermore, the molecular analyses showed that the aogl mutant significantly affected the expression of several genes, which are required for gametogenesis. Our results suggest that AOG1 plays important roles in gameto- genesis at the stage prior to pollen mitosis 1 （PMI） in Arabidopsis, possibly through collaboration with other genes.

Regulation of Reproduction in Delayed Gametophyte of Saccharina japonica (Laminariales, Phaeophyceae): Effects of Light Intensity, Quality and Photoperiod

Saccharina japonica gametophytes can survive a long period under unfavorable environmental conditions,while they also delay in growth and/or reproduction.Although the reproduction in delayed gametophyte of S.japonica was known to be strongly influenced by light intensity,light quality,and photoperiod,no previous studies have evaluated their interactive effects on gametogenesis.To evaluate these effects,we used an orthogonal experiment to expose delayed gametophytes of S.japonica to different light intensities,light qualities,and photoperiods for 12 days.The results showed that changes in light intensity rather than light quality and photoperiod significantly affected the relative growth rates of the delayed gametophytes.Blue light had the greatest promotion on reproduction rate.The optimal light conditions in the early vegetative growth phase in gametogenesis induction for the delayed gametophytes were at 60–80μmol photons m^(−2) s^(−1) with daylength of 12 or 16 hours under white or blue light.When the delayed gametophytes were maintained in a constant light condition from delayed state to gametogenesis,the beneficial photoperiods for vegetative growth and reproductive rate were both 16L(16 hours of light):8D(8 hours of dark).However,when the delayed S.japonica gametophytes achieve the optimal growth state during the first 6 days and then they were cultured at different light conditions for the following 6 days,the reproduction rate increased as the daylength decreased and attained a peak value in group of 8L:16D photoperiod,indicating that photoperiod adjustment at the transition period is crucial in the gametogenesis induction process of delayed gametophyte of S.japonica.

Protective effect of ascorbic acid on cyclophosphamide induced testicular gametogenic and androgenic disorders in male rats

Aim: To study the detrimental effects of cyclophosphamide on the testicular androgenic and gametogenic activities through endocrine inhibition and/or induction of oxidative stress in male albino rats and to evaluate the protective effect of ascorbic acid. Methods: The testicular △~5, 3β-hydroxysteroid dehydrogenase (HSD), 17β-HSD, peroxidase and catalase activities along with the levels of malondialdehyde (MDA) and conjugated dienes in testicular tissue were measured for the evaluation of testicular oxidative stress. The plasma testosterone (T) level was measured by immunoassay. Various germ cells at stage Ⅶ of spermatogenic cycle were quantified from testicular stained sections. Results: Cyclophosphamide treatment results in a significant inhibition in the testicular △~5, 3β-HSD and 17β-HSD activities, a decrease in plasma T level and a diminution in the counts of various germ cells. Moreover, this treatment was also associated with a significant inhibition of the peroxidase and catalase activities along with high levels of MDA and conjugated dienes in the testis. All these changes were reversed by ascorbic acid co-administration. Conclusion: Cyclophosphamide treatment at the dosage used caused testicular gametogenic and androgenic disorders as well as induced testicular oxidative stress that can be reversed by ascorbic acid co-administration.

STUDY ON GAMETOPHYTE VEGETATIVE GROWTH OF UNDARIA PINNATIFIDA AND ITS APPLICATIONS

When cultured under certain environmental coriditions (25℃, light intensity 80 μmol/m2 ·s, LD12/12, in enriched seawater medium with 7 × 10-4mol/L NO3,-N, 1.56× 10-4mol/L, PO4-P and supplementsof other elements like Mn, Fe, I, etc.), mate and female gametophytes of U pinnatifida keptgrowing vegetatively and propagated fast at average daily fresh weight increase rate of about 20%. Theempirical formula Gm=Go. 3m was established to estimate the output of vegeative gametophytes. Vigorousvegetative gametophyte cells began to form reproductive structures (oogonium and spermatangium, whenthe tmperature was lower than 25℃ and other environmental factors wrre kept optimal. The sufficientsupply of gametophyte cells provided enough seeds for raising Undaria sporelings on prodiction scale.Controlled cross-breeding experiments using selcted male and female gametophyte clones which increasetheir cell number by mitosis instead of meiosis were also carried out in vitro. Juvenile sporophytes fromthe

Reproductive polyphenism and its advantages in aphids:Switching between sexual and asexual reproduction

Reproductive polyphenism,which allows one genotype to produce sexual and asexual morphs,is an extreme case of phenotypic plasticity and is commonly observed in aphids.Aphids are typical species that switch these reproductive modes,and the pathway orientation is triggered by the environmental conditions(mainly photoperiod and temperature).The typical arm ual life of aphids in eludes a successi on of parthenogenetic gen erations duri ng the spri ng and summer and a single sexual generation in autumn.In this review,we describe how the environmental cues orientate the reproductive mode of aphids from photoperiodic perception to endocrine regulation,and how juvenile hormones may act on the target cells(oocytes)to initiate the gametogenesis and embryogenesis in sexual and asexual reproduction.We also discuss the paradox of sex,especially the advantages of sexual reproduction in aphids.With the recent development of genomic resources in aphids,many potential genes involved in the reproductive polyphenism will enter the public's awareness.In particular,we describe a novel RNAi method in aphids,which may provide a molecular technique for determining the developmental fate and multiple reproductive strategies.

Expression Characteristics of Odf3 in Gonad Are Different Between Chlamys farreri and Vertebrates

Outer dense fibers are specific subcellular components of mammal sperm flagella, apart from the axoneme and its associated proteins. As one of the outer dense fibers components, ODF3 is essential for the formation of mammal sperm flagella. In the present study, we isolated the Odf3 gene, 1033 bp in length, from Zhikong scallop Chlamys farreri, which was named as Cf-Odf3. It was predicted that Cf-Odf3 encodes a protein of 240 amino acids which contains 5 discontinuous Pro-Gly-Pro repeats. The Cf-Odf3 transcripts were detected in both testis and ovary of C. farreri at various stages through q RT-PCR. The Cf-ODF3 protein synthesized by prokaryotes was purified using Ni^(2+)-NTA affinity chromatography and used to produce its polyclonal antibody. The antibody product was effective and specific as was examined by Western blotting. The Cf-Odf3 transcript and Cf-ODF3 protein were located in intragonadal somatic cells(ISCs), spermatogonia and spermatocytes of C. farreri testes, while no transcription of Cf-Odf3 and synthesis of Cf-ODF3 were detected in spermatids and spermatozoa. The location of Odf3 expression is different from that of vertebrates where ODF3 is synthesized specifically in spermatids and sperm flagella. Moreover, the Cf-Odf3 expression was also detected in ISCs, oogonia and oocytes of the scallop ovaries. Our finding revealed a different characteristic of Odf3 expression between scallop and vertebrates, which implied that Cf-Odf3 played a role in the gametogenesis of C. farreri.

Epigenetics in the etiology and management of infertility

BACKGROUND Epigenetic disruptions have been implicated in some cases of infertility and can serve as therapeutic targets.However,the involvement of epigenetics in infertility has not received adequate attention.AIM This study aimed to determine the epigenetic basis of infertility in order to enhance public knowledge.METHODS Relevant articles on the subject were collected from PubMed,RCA,Google Scholar,SpringerLink,and Scopus.The articles were pooled together and duplicates were removed using Endnote software.RESULTS Available information shows that epigenetic mechanisms,mainly DNA methylation,histone modification,and microRNA interference are necessary for normal gametogenesis and embryogenesis.As a result,epigenetic disruptions in genes that control gametogenesis and embryogenesis,such as DDX3X,ADH4,AZF,PLAG1,D1RAS3,CYGB,MEST,JMJD1A,KCNQ1,IGF2,H19,and MTHFR may result in infertility.Aberrant DNA methylation during genomic imprinting and parental epigenetic mark erasures,in particular,may affect the DNA epigenomes of sperm and oocytes,resulting in reproductive abnormalities.in the sperm may also cause reproductive abnormalities.Furthermore,overexpression or repression of certain microRNAs embedded in the ovary,testis,embryo,as well as granulosa cells and oocytes may impair reproduction.Male infertility is characterized by spermatogenesis failure,which includes oligozoospermia,asthenozoospermia,and teratozoospermia,while female infertility is characterized by polycystic ovary syndrome.Some epigenetic modifications can be reversed by deactivating the regulatory enzymes,implying that epigenetic reprogramming could help treat infertility in some cases.For some disorders,epigenetic drugs are available,but none have been formulated for infertility.CONCLUSION Some cases of infertility have an epigenetic etiology and can be treated by reversing the same epigenetic mechanism that caused it.As a result,medical practitioners are urged to come up with epigenetic treatments for infertility that have an epigenetic cause.

Four Closely-related RING-type E3 Ligases,APD1-4,are Involved in Pollen Mitosis II Regulation in Arabidopsis

Ubiquitination of proteins is one of the critical regulatory mechanisms in eukaryotes. In higher plants, protein ubiquitination plays an essential role in many biological processes, including hormone signaling, photomorphogenesis, and pathogen defense. However, the roles of protein ubiquitination in the repro- ductive process are not clear. In this study, we identified four plant-specific RING-finger genes designated Aberrant_Pollen Development 1_ （APD1） to APD4, as regulators of pollen mitosis II （PMII） in Arabidopsis thaliana （L.）. The apdl apd2 double mutant showed a significantly increased percentage of bicellular-like pollen at the mature pollen stage. Further downregulation of the APD3 and APD4 transcripts in apdl apd2 by RNA interference （RNAi） resulted in more severe abnormal bicellular-like pollen phenotypes than in apdl apd2, suggesting that cell division was defective in male gametogenesis. All of the four genes were expressed in multiple stages at different levels during male gametophyte development. Confocal analysis using green florescence fusion proteins （GFP） GFP-APD1 and GFP-APD2 showed that APDs are associated with intracellular membranes. Furthermore, APD2 had E2-dependent E3 ligase activity in vitro, and five APD2-interacting proteins were identified. Our results suggest that these four genes may be involved, redundantly, in regulating the PMII process during male gametogenesis.

Control of PHERES1 Imprinting in Arabidopsis by Direct Tandem Repeats

Genomic imprinting is an epigenetic phenomenon that causes monoallelic expression of specific genes dependent on the parent-of-origin. Imprinting of the Arabidopsis gene PHERES1 requires the function of the FERTILIZATION INDEPENDENT SEED （FIS） Polycomb group complex as well as a distally located methylated region containing a tandem triple repeat sequence. In this study, we investigated the regulation of the close PHERES1 homolog PHERES2. We found that PHERES2 is also a direct target gene of the FIS Polycomb group complex, but, in contrast to PHERES1, PHERES2 is equally expressed from maternal and paternal alleles. Thus, PHERES2 is not regulated by genomic imprinting, correlating with the lack of tandem repeats at PHERES2. Eliminating tandem repeats from the PHERES1 locus abolishes PHERES1 imprinting, demonstrating that tandem repeats are essential forPHERES1 imprinting. Taking these results together, our study shows that the recently duplicated genes PHERES1 and PHERES2 are both target genes of the FIS Polycomb group complex but only PHERES1 is regulated by genomic imprinting, which is likely caused by the presence of repeat sequences in the proximity of the PHERES1 locus.

The Anaphase-Promoting Complex/Cyclosome in Control of Plant Development

Temporal controlled degradation of key cell division proteins ensures a correct onset of the different cell cycle phases and exit from the cell division program. In light of the cell cycle, the Anaphase-Promoting Complex/Cyclosome （APC/C） is an important conserved multi-subunit ubiquitin ligase, marking targets for degradation by the 26S protea- some. However, whereas the APC/C has been studied extensively in yeast and mammals, only in the last decade has the plant APC/C started to unveil its secrets. Research results have shown the importance of the APC/C core complex and its activators during gametogenesis, growth, hormone signaling, symbiotic interactions, and endoreduplication onset. In addition, recently, the first plant APC/C inhibitors have been reported, allowing a fine-tuning of APC/C activity during the cell cycle. Together with the identification of the first APC/C targets, a picture emerges of APC/C activity being essential for many different developmental processes.

What we have learned from transcript profile analyses of male and female gametes in flowering plants

Double fertilization is one of the predominant features of sexual reproduction in flowering plants but, because of the physical inaccessibility of gametes, the essential molecular mechanisms in these processes are largely unknown. Based on the techniques for isolating highly purified gametes from several species and well-developed methods for manipulating RNA from limited quantities of gametes, genome-wide investigations of gamete transcription profiles were recently conducted in flowering plants. In this review, we survey the accumulated knowledge on gamete collection and purification, cDNA library construction, and transcript profile analysis to assess our understanding of the molecular mechanisms of gamete specialization and fertilization.