Analysis Of GASA Gene Family In Populus Euphratica And Functional Study Of PeuGASA15 Gene

Plants had to face the complex and changeable natural environment during their growth.To adapt the harsh environment,maintain their own development and resist biological and abiotic stresses,plants have evolved the cascade amplification reaction mechanisms and cell communication mechanisms to integrate the signaling molecular pathways,effectively allocate the limited resources acquired,coordinate the contradiction between growth and stress,resist adverse external environment,and finally maintain the normal growth of plants.GASA proteins are cysteine-rich peptide which widely found in vascular plants.They are involved in regulating plant growth and development,plant hormone response and transduction,and stress response,and may play an important role in coordinating growth and stress.It is great important to identify GASA protein,understand the mechanism of plant resource allocation and to select and improve trees through molecular breeding to obtain stable genetic trees with high yield,high-quality and strong resistance to stress.In this study,the model plant of abiotic stress woody research Populus euphratica was used as the research material to conduct bioinformatics analysis on PeuGASA genes,which encode small peptides involved in growth and development and stress,and PeuGASA15 gene was selected for functional analysis.The results are as follows:(1)Based on the well-sequenced Populus trichocarpa genome,21 Ptr GASA and 19 PeuGASA candidate genes were identified.Through phylogenetic analysis,the selected GASA conserved domains were divided into three subfamilies.The closer the phylogenetic relationship was,the more similar the gene structure of GASA genes and the motifs of GASA proteins in Populus were.The GASA family genes of Populus experienced multiple gene duplication events.The Populus GASA proteins were secretory signal peptide,which located in the cell wall or extracellular region.The transcription levels of GASA genes in young and tender tissues were higher than those in mature tissues.There were abundant cis-acting promoter elements that regulated growth and development and responded to hormones and stress.The PeuGASA genes in P.euphratica leaves were extensively involved in exogenous hormones and drought stress response.(2)The protein encoded by PeuGASA15 gene contained 102 amino acids,and has a typical GASA conserved domain.A large number of cis-acting elements were found in the upstream promoter of PeuGASA15 gene in response to hormone and stress.The recombinant plasmid p CAMbi A1391-PeuGASA15Pro::GUS was obtained and transformed into Arabidopsis.High GUS activity was detected in roots,hypocotyls,cotyledons,leaves,flower stems,petals,sepals,stigmas and stamens of Arabidopsis,especially in their vascular bundle.GUS gene expression was induced by auxin in transgenic Arabidopsis leaves,while inhibited by ABA,D-mannitol and Na Cl.(3)PeuGASA15 gene promoted the seed germination of Arabidopsis,alleviated the inhibition of seed germination caused by ABA and D-mannitol,while did not alleviate the inhibition caused by salt stress.PeuGASA15 gene promoted aboveground biomass accumulation and rosette leaves and roots development in Arabidopsis.PeuGASA15 gene alleviated the ABA inhibited primary root elongation and lateral root initiation of Arabidopsis.PeuGASA15 gene also partially alleviated primary elongation inhibited by salt stress in Arabidopsis.(4)PeuGASA15 gene participated in auxin transport and signaling pathways,affected lignin content and root development,and partially alleviated stem elongation inhibited by high concentration of naphthalene acetic acid(NAA).PeuGASA15 gene alleviated growth inhibition caused by D-mannitol.PeuGASA15 gene cascaded dehydration signal and ABA signal pathway to enhance short-term drought resistance of poplar.Inoculation with anthrax fungus showed that PeuGASA15 gene could inhibit fungal infection in poplar.In addition,PeuGASA15 gene might be involved in auxin signaling pathway,Na~+transport and ROS pathway,alleviating the yellowing and abruption of leaves caused by salt stress and maintaining the normal growth of poplar.PeuGASA15 gene partially alleviated leaf yellowing,adventitious root and lateral root elongation inhibition,and biomass accumulation reduction caused by D-mannitol stress.Peu TTL1-Like protein and PeuGASA15 protein interact to regulate the growth and tolerance mechanism of poplar.(5)Overexpression of PeuGASA8 gene,a homolog of PeuGASA15 gene,also alleviated the growth of aboveground parts of poplar inhibited by high concentration of NAA.PeuGASA8 gene affected root development by reducing main root elongation and promoting lateral root initiation.However,the interaction between Peu TTL1-Like protein and PeuGASA8 protein was not detected by yeast two-hybrid technique.In conclusion,PeuGASA15 gene was involved in hormones signaling pathways,regulated organ growth and development,and responded to biological and abiotic stresses,which provided a theoretical basis for studying the function of PeuGASA genes in the coordination of growth and stress.In addition,PeuGASA15 gene was highly expressed in the vascular tissue,which provided theoretical reference for the involvement of GASA gene family in the development of vascular tissue.