Studies On Developmental Mechanism Of The Natural Alfalfa And Peanut Mutants With Ectopic Leaflets

Legumes are widely distributed throughout the world,provide humanswith protein,oil and vegetables,in addition,some legume species are high-quality pasture.Alfalfa,as thehighqualityforage,has the advantages of high crude protein content in the leaves and easy to digest forlivestock.Peanuts arewidely planted crop in China,and their seeds contain high-quality edible oil and protein.Leaf is the main organ for plant photosynthesis,and photosynthesis is the basis of carbohydrate accumulation.Therefore,the studies of the leaf development mechanism in alfalfa and peanut will not only help us to understand the mechanism of leaf development in legume species,but also helpto improve the leaf pattern and plant architecture by molecular design for increasing the quality and quantity of forage.The adult leaf of alfalfa is trifoliate,but the compound leaf of some natural alfalfa mutants will developted into five leaflets.In this study,we used alfalfa Algonquin as a wild type control to study the compound leaf development mechanism of a natural mutant which developed five leaflets.At the P5 stage,a pair of lateral leaflet primordia was initiated on the base of lateral leaflet primordium,and then developed into five leaflets at the later stage.The expression level of genes involved in compound leaf development was measured by qRT-PCR.The data revealed that the expression of MsKNOX2 and MsSGL1 was significantly increased in the vegetative shootbudsofmutant,implying that the ectopic leaflets in mutant may be caused by the high expression of MsKNOX2 in the vegetative shootbuds.Moreover,MsSGL1 was not only expressed in the SAM and the common leaf primordium,but also expressed in the ectopic lateral leaflet primordia.This data suggests that MsSGL1 may also be involved in the regulation of compound leaf development of mutant.The RNA-seq data showed that the genes in signal transduction and response pathway of cytokinin were differentially expressed between wild type and mutant.Furthermore,we applied the cytokinin on Algonquin,and found that the ectopic leaflets were developed in Algonquin,which resembled the phenotype of mutant alfalfa,suggesting that cytokinin may be involved in the initiation of two ectopic lateral leaflet primordia.In addition,the aboveground weight(freshand dry)of mutant was significantly higher than that of Algonquin,indicating the better biomass produced in mutant.The compound leaf of wild-type peanuts consists of four leaflets.In this study,a peanut mutant with five leafletswasisolated.The observation showed that an ectopict terminal leaflet primordium initiated between the two terminal leaflet primordia at the P3 stage of leaf development,and then developed into the ectopic terminal leaflet.TheRNA-seq data showed thata large number ofdifferentially expressed genes were enriched in GO terms such as anatomical structure development,multicelluar organismal process and multicelluar organismal development,which is consistent with thestatus of rapid division and differentiation of vegetative shootbuds cells.Furthermore,a large number ofgenes related to auxin and cytokinin receptors and response factors are differentially expressed.These preliminary data showed that phenotype of peanut mutant may be related to the changes in auxin and cytokinin pathway in vegetative shoot buds.