Analysis And Gene Mapping Of A Maize Mutant Termed Sk-A7110

The silks that emerge from the end of the maize ear and derive from the pistil pla y a pivotal role in pollination.If the silks fail to develop normally,seed production,and therefore yield,is significantly reduced.Study the genetic mechanisms of the development and morphogenesis of silk is further conducive to the researches on the function of sex-determining genes and key phytohormones involved in maize sex-determination,which has potential application value in maize breeding and hybrid seed production.Previous studies on sex-related mutants have revealed that phytohormones controlled by sex determination genes play an important role in the regulation of maize flower organogenesis.Brassinosteroids(BRs),cytokinins(CKs),gibberellins acid(GA)and jasmonate acid(JA)are the four main phytohormones involved in sex determination,and endogenous GA is crucial for the development of ovules and silks.Processes that determine pistil fate is core content of maize flower development,in which SK1 is required to protect pistil primordia from a cell death signal produced by TS1 and TS2,and Rmr6 was proven to play an important role in regulating the functions of SK1.sk-A7110 was a natural mutant found in inbred lines A7110,and its silk-absence trait can be inherited.Here we named the key gene determining silk development SKA7110.In this study,we observed and identified the phenotype of sk-A7110,analyzed the genetic characteristics of the mutant trait.We also mapped SKA7110 gene on chromosome 2 by map-based cloning.Main results are addressed below.1.sk-A7110 only lost silks in the early period of ear development and have normal tassel with functional pollen and is normal in other parts.2.We investigated the F1 and BC1 populations of the hybridized combinations between sk-A7110 as the male and inbredlines 80044,B73,and P2 as the female.All of the F1 individuals had normal ear with silks,and a segregation ratio that mutant: wild-type = 1: 1 was observed in all BC1 populations of the three hybridized combinations,which approved that the absence of silks in sk-A7110 plants was caused by a single recessive nucleus gene.3.SKA7110 gene was mapped on chromosome 2S,and linked with the markers umc1555 and umc1448,with 2.24 c M to umc1555 and 6.72 cM to umc1448.The fine mapping works helped to map SKA7110 to a 0.94 cM region between the newly developed markers IDP1453 and SAG21,in which the physical distance is about 255 kb and five genome annotated genes are labeled.