Identification Of Potato NF-YB Family Genes And Functional Characterization Of StNF-YB3.1 In Potato (Solanum Tuberosum L.)

Nuclear factor Y(NF-Y)is one of the most ubiquitous transcription factors(TFs),comprising NF-YA,NF-YB and NF-YC subunits,and has been identified and reported in various aspects of development and environment stress in plants.In the present study,we isolated 20 genes encoding NF-YB proteins in an analysis of the potato(Solanum tuberosum L.)genome.The 20 StNF-YB genes were distributed on 8 of the 12 potato chromosomes.Phylogeny analysis indicated the 20 StNF-YB genes clustered into five distinct clades.Multiple alignments showed that StNF-YB proteins had highly-conserved core regions and relatively variable N-terminal or C-terminal domains.RNA-seq data showed that the StNF-YB genes had specific expression patterns in various tissues and in response to abiotic stresses.StNF-YB3.1,closest to AtNF-YB3,OsNF-YB11/HAP3H and TaNF-YB3,was selected for detailed functional studies.The full-length cDNA of StNF-YB3.1 was cloned by rapid amplification of cDNA ends(RACE)method.StNF-YB3.1 was constitutively expressed in various organs.Overexpression of StNF-YB3.1 in potato(cv.Atlantic)resulted in accelerated onset of flowering,and significant increase in leaf chlorophyll content in field trials.However,transgenic potato plants overexpressing StNF-YB3.1(OEYB3.1)showed significant decreases in photosynthetic rate and stomatal conductance both at tuber initiation and bulking stages.OEYB3.1 lines were associated with significantly fewer tuber numbers and yield reduction.Guard cell size and stomatal density were not changed in OEYB3.1 plants,whereas ABA-mediated stomatal closure was accelerated compared to that of wild type plants because of the up-regulation of genes for ABA signaling,such as StCPK 10-like,StSnRK2.6/OST1-like,StSnRK2.7-like and StSLAC1-like.We speculate that the acceleration of stomatal closure was a possible reason for the significantly decreased stomatal conductance and photosynthetic rate.