Polyploidy events shaped the expansion of transcription factors in Cucurbitaceae and exploitation of genes for tendril development

Cucurbitaceae is one of the most important plant families distributed worldwide.Transcription factors(TFs)regulate plant growth at the transcription level.Here,we performed a systematic analysis of 42641 TFs from 63 families in 14 Cucurbitaceae and 10 non-cucurbit species.Whole-genome duplication(WGD)was the dominant event type in almost all Cucurbitaceae plants.The TF families were divided into 1210 orthogroups(OGs),of which,112 were unique to Cucurbitaceae.Although the loss of several gene families was detected in Cucurbitaceae,the gene families expanded in five species that experienced a WGD event comparing with grape.Our findings revealed that the recent WGD events that had occurred in Cucurbitaceae played important roles in the expansion of most TF families.The functional enrichment analysis of the genes that significantly expanded or contracted uncovered five gene families,AUX/IAA,NAC,NBS,HB,and NF-YB.Finally,we conducted a comprehensive analysis of the TCP gene family and identified 16 tendril-related(TEN)genes in 11 Cucurbitaceae species.Interestingly,the characteristic sequence changed from CNNFYFP to CNNFYLP in the TEN gene(Bhi06M000087)of Benincasa hispida.Furthermore,we identified a new characteristic sequence,YNN,which could be used for TEN gene exploitation in Cucurbitaceae.In conclusion,this study will serve as a reference for studying the relationship between gene family evolution and genome duplication.Moreover,it will provide rich genetic resources for functional Cucurbitaceae studies in the future.

Functional Diversity of CYCLOIDEA-like TCP Genes in the Control of Zygomorphic Flower Development in Lotus japonicus

CYCLOIDEA （CYC）-like TCP genes play key roles in dorsoventral differentiation of zygomorphic flowers in Papilionoideae legumes. In this study, we analyzed the kew mutants whose flowers lost lateral identity, and investigated the diverse functions of three LjCYC genes during zygomorphic flower development in the model legume Lotus japonicus. We showed that kew1 and kew3 are allelic mutants of LjCYC3, a CYC-like TCP gene. Through transgenic experiments, it was shown that LjCYC1 possesses dorsal activity similar to LjCYC2, and that LjCYC3 alone is sufficient to confer lateral activity, and an epistatic effect between dorsal and lateral activities was identified. Sequence analysis revealed a striking alteration at the 3 end of the LjCYC3 open reading frame （ORF） in comparison with those of LjCYC1 and LjCYC2 ORFs. Furthermore, it was found that LjCYC proteins could interact with each other and possess different activities by means of a transcriptional activity assay. Our data demonstrate that the sequence variation and the subsequent alteration of protein property play important roles in the functional diversity of different LjCYC genes in controlling zygomorphic flower development in Lotus japonicus.

Petal Development in Lotus japonicus

Previous studies have demonstrated that petal shape and size in legume flowers are determined by two separate mechanisms, dorsoventral （DV） and organ internal （IN） asymmetric mechanisms, respectively. However, little is known about the molecular mechanisms controlling petal development in legumes. To address this question, we investigated petal development along the floral DV axis in Lotus japonicus with respect to cell and developmental biology by comparing wild-type legumes to mutants. Based on morphological markers, the entire course of petal development, from initiation to maturity, was grouped to define 3 phases or 13 stages. In terms of epidermal micromorphology from adaxial surface, mature petals were divided into several distinct domains, and characteristic epidermal cells of each petal differentiated at stage 9, while epidermal cells of all domains were observed until stage 12. TCP and MIXTA-like genes were found to be differentially expressed in various domains of petals at stages 9 and 12. Our results suggest that DV and IN mechanisms interplay at different stages of petal development, and their interaction at the cellular and molecular level guides the elaboration of domains within petals to achieve their ideal shape, and further suggest that TCP genes determine petal identity along the DV axis by regulatincl MIXTA-like clene expression.