J-family genes redundantly regulate flowering time and increase yield in soybean

Soybean(Glycine max)is a short-day crop whose flowering time is regulated by photoperiod.The longjuvenile trait extends its vegetative phase and increases yield under short-day conditions.Natural variation in J,the major locus controlling this trait,modulates flowering time.We report that the three J-family genes influence soybean flowering time,with the triple mutant Guangzhou Mammoth-2 flowering late under short days by inhibiting transcription of E1-family genes.J-family genes offer promising allelic combinations for breeding.

Parallel selection of distinct Tof5 alleles drove the adaptation of cultivated and wild soybean to high latitudes

Photoperiod responsiveness is a key factor limiting the geographic distribution of cultivated soybean and its wild ancestor.In particular,the genetic basis of the adaptation in wild soybean remains poorly understood.In this study,by combining whole-genome resequencing and genome-wide association studies we identified a novel locus,Time of Flowering 5(Tof5),which promotes flowering and enhances adaptation to high latitudes in both wild and cultivated soybean.By genomic,genetic and transgenic analyses we showed that Tof5 en-codes a homolog of Arabidopsis thaliana FRUITFULL(FUL).Importantly,further analyses suggested that different alleles of Tof5 have undergone parallel selection.The Tof5H1 allele was strongly selected by humans after the early domestication of cultivated soybean,while Tof5H2 allele was naturally selected in wild soybean,and in each case facilitating adaptation to high latitudes.Moreover,we found that the key flowering repressor E1 suppresses the transcription of Tof5 by binding to its promoter.In turn,Tof5 physically associates with the promoters of two important FLOWERING LOCUS T(FT),FT2a and FT5a,to upregulate their transcription and promote flowering under long photoperiods.Collectively,ourfindings provide insights into how wild soybean adapted to high latitudes through natural selection and indicate that cultivated soybean underwent changes in the same gene but evolved a distinct allele that was artificially selected after domestication.

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.

SERK Family Receptor-like Kinases Function as Co-receptors with PXY for Plant Vascular Development

In Arabidopsis, the CLAVATA3/EMBRYO SURROUNDING REGION-RELATED （CLE） peptides play important roles in regulating proliferation and differentiation of plant-specific stem cells. Although receptors of CLEs are reported to be leucine-rich repeat receptor kinases, the mechanisms underlying CLE-induced receptor activation remain largely unknown. Here we show that SOMATIC EMBRYOGENESIS RECEPTOR KINASEs （SERKs） serve as co-receptors in CLE41/TDIF-PXY signaling to regulate plant vascular development. TDIF induces interaction of its receptor PXY with SERKs in vitro and in vivo. Furthermore, the serk1-1 serk2-1 bakl-5 mutant plants are less sensitive to TDIF, phenocopying the pxy mutant with a compromised promotion of procambial cell proliferation. Crystal structure of the PXY-TDIF-SERK2 complex reveals that the last amino acid of TDIF conserved among CLEs and other evolutionary-related peptides is important for the interaction between SERK2 and PXY. Taken together, our current study identifies SERKs as signaling components of the TDIF-PXY pathway and suggests a conserved activation mechanism of CLE receptors.

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.

The Features and Regulation of Co-transcriptional Splicing in Arabidopsis

Precursor mRNA(pre-mRNA)splicing is essential for gene expression in most eukaryotic organisms.Previous studies from mammals,Drosophila,and yeast show that the majority of splicing events occurs co-transcriptionally.In plants,however,the features of co-transcriptional splicing(CTS)and its regulation still remain largely unknown.Here,we used chromatin-bound RNA sequencing to study CTS in Arabidopsis thaliana.We found that CTS is widespread in Arabidopsis seedlings,with a large proportion of alternative splicing events determined co-transcriptionally.CTS efficiency correlated with gene expression level,the chromatin landscape and,most surprisingly,the number of introns and exons of individual genes,but is independent of gene length.In combination with enhanced crosslinking and immunoprecipitation sequencing analysis,we further showed that the hnRNP-like proteins RZ-1B and RZ-1C promote efficient CTS globally through direct binding,frequently to exonic sequences.Notably,this general effect of RZ-1B/1C on splicing promotion is mainly observed at the chromatin level,not at the mRNA level.RZ-1C promotes CTS of multiple-exon genes in association with its binding to regions both proximal and distal to the regulated introns.We propose that RZ-1C promotes efficient CTS of genes with multiple exons through cooperative interactions with many exons,introns,and splicing factors.Our work thus reveals important features of CTS in plants and provides methodologies for the investigation of CTS and RNA-binding proteins in plants.