Preliminary Analysis Of Function For Candidate Nulliplex-branch Gene In Cotton

Cotton is an important economic crop,and plant architecture is an important agronomic factor influencing cotton yield level.Most of the cotton varieties show normal fruiting branch,which usually contain more than two branch nodes.In cotton,a type of mutant called Nulliplex-Branch(NB)was found in upland cotton(Gossypium hirsutum)and Pima cotton(G.barbadense).The fruiting branch of NB cotton showing determinate growth,and flowers sometimes directly developed from the leaf axils of the main stem.Furthermore,NB mutants usually flower earlier than normal branch type.NB cotton was considered to be a useful germplasm because it is suitable for high-density planting without pruning and chemical regulation.Therefore,cloning and characterization of genes responsing for NB trait contribute to the genetic utilization of nulliplex-branch fruiting traits.In our former study,NB gene was located in an 600Kb-wide interval on chromosome D7 by molecular marker mapping,which contained a CENTRORADIALIS(CEN)homolog.The cen mutant in snapdragon displayed limited growth with a top flower.We speculated that the CEN homolog in this interval was the candidate gene causing the NB in cotton.NB gene was named GhCEN thereafter.In this study,sequence characteristic and expression mode of GhCEN was analyzed in different cotton lines,and effect of it on flowering time and plant architecture was investigated by ectopic expression in Arabidopsis thaliana.The main results are as follows:1 The results showed that there was a single base mutation in the P133 S locus,which was the conserved locus of the CEN homologous gene,and the mutations of the GhCEN may lead to the function loss,so the nulliplex-branch fruiting traits show recessive inheritance.2 The expression pattern of GhCEN gene was analyzed by quantitative RT-PCR.The results showed that the expression level of GhCEN was the highest in the root,and it was also enriched at the stem apex.The mRNA abundance of GhCEN gene was very low and did not show change with the leaf age.The results showed that the different photoperiod treatments under long day treatment(16h),roots and leaves are light culture synthesis under the condition of GhCEN,and showed circadian variation;short day treatment(8h),GhCEN gene expression in leaves were significantly higher than the expression in the root.3 Overexpression of GhCEN and cen with 35 S promoter respectively caused early flowering in transgenic Arabidopsis.The nulliplex-branch fruiting mutant in cotton showed early flowers also,so GhCEN may be subject to different genetic regulation in Arabidopsis thaliana and cotton.