Identification And Function Analysis Of GhPSY In Arabidopsis Thaliana And Gossypium Hirsutum

Plant peptide hormone is a new kind of plant hormone.It played an important role in regulating physiological processes of plant,for example,growth,development,metabolism,etc.PSY1(plant peptide containing sulfated tyrosine 1)was a tyrosine sulfated glycopeptide,which could promote the proliferation and expansion of plant cells.To explore the biological functions of Gh PSY,PSY family genes of Gossypium hirsutum were identified at the whole genome level.At the same time,the structure and expression pattern of PSY gene of Gossypium hirsutum were analyzed.Then the biological function of Gh PSY was confirmed by Arabidopsis mutants.Finally,the effect of Gh PSY on the development of cotton plants and fiber cells were studied by up-regulating and down-regulating Gh PSY in Gossypium hirsutum.The main results are as follows:1.Identification and bioinformatics analysis of PSY genes in Gossypium hirsutumIn this study,ten homologous genes of PSY were identified from the whole genome database of Gossypium hirsutum.The phylogenetic trees of PSY from Arabidopsis thaliana and Gossypium hirsutum were constructed by MEGA7.PSY gene was divided into two sub-clades(Ⅰand Ⅱ).The protein encoded by PSY gene is a precursor peptide composed of 65-100 amino acids.A conserved signal peptide domain,L-FL-SS region,could be predicted at the N-terminal of the peptide.The C-terminal contains a conserved mature PSY peptide region,which is composed of 15-18 amino acids,namely DY-AN-HDP region.2.Expression pattern analysis of Gh PSY1 and Gh PSY5 in various tissues and organs of Gossypium hirsutum and cloning of their promotersTo explore the spatiotemporal expression pattern of Gh PSY,the expression level of Gh PSY1 and Gh PSY5 were analyzed in different tissues and organs of Gossypium hirsutum.Gh PSY was widely expressed in tissues and organs of Gossypium hirsutum,and had dominant expression in roots.The expression of Gh PSY1 was high in 20 d fiber and the ovule of late development,but low in other tissues.Gh PSY5 was mainly expressed in fast-growing fibers,but also in young stems,leaves,cotyledons,pistils and hypocotyls.The results of histochemical analysis of the transgenic plants with p PSY1::GUS and p PSY5::GUS showed that Gh PSY1 and Gh PSY5 were expressed in leaves,roots,pods,etc.3.Heterologous expression of Gh PSY promotes root elongation and the increase of fresh weight of Arabidopsis thalianaIn order to further explore the physiological func tion of Gh PSY,35 S promoter-driven superexpression vectors were constructed and transgenic pure lines of Gh PSY1 and Gh PSY5 with single copy were obtained from Arabidopsis thaliana.Compared with the wild type,heterologous expression of Gh PSY1 and Gh PSY5 could promote the growth of main root and the increase of above-ground biomass.The results of fluorescence microscopy showed that both Gh PSY1 and Gh PSY5 promoted root elongation by increasing the number of cells.4.Effects of regulation of Gh PSY1 on number and early elongation of fiberIn order to explore the function of Gh PSY1,the expression of the gene was respectively down-regulated and up-regulated in Gossypium hirsutum.The results showed that vegetative growth of plants would be inhibited if we down-regulated the expression of Gh PSY1 of Gossypium hirsutum.the expression of the gene up-regulated could not only increase the number of fibers,but also promote the elongation of early fiber cell,but also shorten the length of mature fibers.In addition,the expression of Gh PSY1 up-regulated could also increase coat finger of the fiber and seed finger of the ovule.5.Effect of Gh PSY up-regulated on growth rate of cotton plantIn order to investigate the function of Gh PSY5,the expression of the gene was up-regulated in Gossypium hirsutum.The results showed that the growth of cotton plants could be promoted by Gh PSY5 up-regulated.Meanwhile,the expression of Gh PSY5 up-regulated could not only increase the number of fibers,but also promote the elongation of early fiber cell,but also shorten the length of mature fibers.In addition,the expression of Gh PSY5 up-regulated could also increase coat finger of the fiber and seed finger of the ovule.