Functional Identification Of Medicago Truncatula MtSOC1 Gene

Florescence is crucial to plants,and understanding its regulation mechanism will help improve crop yields.Medicago truncatula is a self-pollinating diploid legume crop that has several advantages as a model forage plant,such as a small genome and mature genetic transformation systems.Florescence is one of the key factors affecting forage yield.However,research on the molecular mechanism underlying florescence regulation has mainly concentrated on non-forage plants,such as Arabidopsis.Only limited information about the regulation of florescence in forage crops has been obtained,mainly from M.truncatula.This lack of knowledge has severely restricted the use of genetic modification methods when attempting to produce high-yielding forage crop varietiesSOC1,a MADS-box transcription factor,is commonly considered to be one of the critical factors involved in the regulation of plant flowering.In order to clarify the florescence regulation mechanism,MtSOC1 was screened from ufo mutant transcriptome data,which is a mutant that exhibits abnormal floral organ development.A total of four MtSOC1 homologs:MtSOC1-1,MtSOC1-2,MtSOC1-3,and MtSOC1-4,were obtained.Evolutionary analysis and tissue-specific expression analysis showed that MtSOC1-1 was significantly correlated with flowering.Therefore,further studies were undertaken to verify its function and regulation mechanism.The main conclusions were as follows(1)MtSOC1-1 encodes a typical M.truncatula SOC1 factor and is closely related to flowering Four MtSOC1 genes were screened from the ufo mutant transcriptome data.Sequence alignment analysis showed that all four MtSOC1 genes had a MADS box and a K-Box,which are often found in SOC1 homologs.The phylogenic analysis confirmed that the four MtSOC1 proteins were closely related to known SOC1 factors,which suggested that they have similar functions during the regulation of M.truncatula florescence.A tissue-specific expression analysis revealed that MtSOC1-1 was most highly expressed in flowers,which suggested that it was strongly related to florescence(2)MtSOC1-1-overexpressing M.truncatula lines produced phenotypes that showed abnormally early flowering and abnormal leaf and fruit morphogenesis.Subcellular localization revealed that MtSOC1-1 was located in the nucleus of Nicotiana tabacum leaves,which suggested that MtSOC1-1 is a transcriptional regulator.It is also possible to locate in the membrane or cytoplasm.In MtSOC1-1-overexpressing M.truncatula plants,the flowers,leaves,and fruits exhibited abnormalities In particular,these plants showed an early flowering phenotype.Cut sections indicated that the ovary cells were closer together,and the epidermis hairs on the leaves,pods,and seeds had not developed correctly.For example,the plants had fewer prickles,smaller seeds,and a blackened pod color.Furthermore,the four MtSOC1 genes were all upregulated in transgenic plants under long-day conditions.However,there were no significant changes compared to the wild type under short-day conditions,which suggested that MtSOC1-1 was involved in the response to photoperiod,and that this was part of the flower regulation process.(3)MtSOC1-1 mainly regulated flowering by affecting the photoperiod pathways.Additionally,MtSOC1-1 might regulate ABA and the auxin signal transduction pathways,which would affect pod and seed development.An analysis of the transcriptome data from MtSOC1-1 overexpressing plants showed that several key photoperiod genes,such as COP1,PHYA,CRY1,and CRY2.COP1,and PHYA,were significantly upregulated.However,CRY1 and CRY2 were significantly downregulated.Furthermore,80 photosynthesis genes and six photosynthesis-antenna-encoding genes were significantly differentially expressed,which suggested that they probably played a role in florescence regulation.The results also showed that seven ABA signal transduction genes were differentially expressed.These consisted of four upregulated PP2Cs,and three downregulated PYLs.Five auxin signal transduction genes were also differentially expressed.IAA and ARF were upregulated,and two SAURs and CH3 were downregulated.These genes,which are related to ABA and auxin signal transduction,might explain why seed development was abnormal.Target gene prediction showed that PP2C,PYL,SAUR,and CH3 were directly targeted by MtSOC1-1.However,further studies are needed to elucidate the regulatory mechanism.In conclusion,this study revealed that MtSOC1-1 is involved in the regulation of florescence,SOC1 homologs production,and leaf and seed development.A multiple high-throughput data analysis showed that MtSOC1-1 was also involved in photoperiod regulation,ABA synthesis,and transduction pathways,which means that it plays an important role in M.truncatula development.These results could be used to improve legume breeding.