Evolution,Expression And Function Analysis Of INV Gene Family In Saccharum Spontaneum And Saccharum Officinarum

Sugarcane(Saccharum spp.)is one of the most important sugar crops all over the world and also the feedstock of biofuel.The mature sugarcane stem has sucrose content while invertase genes play an important role in the process of sucrose metabolism.Investigating the genomics and gene function of invertase genes plays an essential role in comprehending sucrose accumulation and the improvement of quality in sugarcane.We identified the invertase gene family in Saccharum spontaneum and Saccharum officinarum based on comparative genomics.And we further analyzed their evolution and expression pattern to provide knowledge and genomic resources for molecular breeding in sugarcane.The main findings are listed as follows.(1)19 invertase genes were identified using comparative genomics based on the invertase genes in Sorghum bicolor and Arabidopsis thaliana.Invertase genes in Saccharum spontaneum contained 53 pairs of alleles while invertase genes in Saccharum officinarum contain 79 pairs of alleles.The invertase genes in sugarcane and sorghum were divided into branch Ⅰ,Ⅱ and Ⅲ by phylogenetic analysis.Gene structure and motif analysis indicated that there were 15 motifs and 2 to 7 exons in invertase genes in two sugarcane species.Invertase genes in Saccharum spontaneum contained 6 pairs of tandem duplicate genes and 58 pairs of segmental duplicate genes while the invertase genes in Saccharum officinarum contain 29 pairs of tandem duplicate genes and 163 pairs of segmental duplicate genes,both indicating segmental duplications play a dominant role in the evolutionary process of invertase genes in sugarcane.All of the Ka/Ks value of the duplicated invertase genes in two sugarcane species were lower than 1 except Ss CWINV9-1/Ss CWINV9-2,So VINV2-1/ So VINV2-5,So CWINV10-1/So CWINV10-2 and So CWINV5-2/ So CWINV5-9,indicating that the duplicated invertase genes in two sugarcane species had undergonet purifying selection.(2)The expression patterns of invertase genes in different tissues in sugarcane indicated that Ss VINV1-2 and Ss VINV1-3expressed highly in stem in Saccharum spontaneum while So VINV1-4,So N/AINV14-6 and So N/AINV17-1 expressed highly in leaves in Saccharum officinarum,which suggested that they are the main functional genes and play an essential role in the growth and development in sugarcane.Ss VINV1-2 and Ss VINV1-3 expressing highly in the young stem of sugarcane suggested that they may transport sucrose apoplast to make it hydrolyze into fructose and glucose and promote the growth of sugarcane stem by compounding cellulose and facilitating respiration,which was involved in the growth and development in sugarcane.So VINV1-4 and So N/AINV14-6 expressed increasingly as approaching the top of sugarcane leaves,which indicated that they might be associated with the photosynthesis of sugarcane leaves.A high similarity of the expression patterns of homologous invertase genes existed in two sugarcane species.Homologous genes INV1,INV4 and INV17 expressed highly both in sugarcane stem and leaves.The promoter analysis of homologous invertase genes in two sugarcane species indicated that there was a missing promoter fragment of 242 base pair in INV1 gene promoter in Saccharum officinarum.The INV1 gene promoter included cis-elements involved with light response,auxin and drought induction,such as CAAT-box,TGA-element,GTGGC motif and MBS,suggesting that the promoter might be associated with the growth,stem formation and development in sugarcane.(3)Yeast-one hybrid assay identified some regulatory proteins interacted with Ss INV1 promoter,including osmotin,sucrose synthase 1,b ZIP,flowering locus T and PPCI proteins.Sucrose synthase 1 protein supply UDP glucose and fructose,suggesting that the interaction between Ss INV1.2 and sucrose synthase 1 might contribute to the difference of sucrose content in two sugarcane species.Flowering locus T protein could induce flowering by regulating APETALA1 gene,which could regulate the process from growing to flowering in plant.The PPCI protein interacted with Ss INV1.4 had multiple functions.For instance,it could control cell division and elongation in the developmental process in plant by participating in cytokinin and auxin mediated signaling pathways.And it also could regulate the nuclear targeting after cell division through controlling NAC089 transcription factor.The interaction between PPCI and Ss INV1.4 could influence the cell division and plant growth by participating the cytokinin and auxin mediated signaling pathways,eventually resulting in the differences of plant height and stem in two sugarcane species.(4)p Ss INV1:GUS expression vector was observed to express prominently in the anther in Arabidopsis thaliana except in stem and leaves,indicating the expression pattern of p Ss INV1:GUS vector was tissue-specific.The results suggested that Ss INV1 promoter might play an important role in the process of formation of anther and flowering in plant.