The Mechanism Of Brassinosteroid And HY5 Induced Gibberellin Regulating Leaf And Stem Elongation In Tomato Under Low Proportion Of Red Light And Far Red Light

Tomato(Solarium hycopersicum)is one of the most important vegetables cultivated in the facility,its growth and development is more susceptible to external conditions.The light and temperature conditions of facility cultivation are more likely to induce stem elongation and affect its yield and quality.Although plant hormones such as gibberellin,auxin,etc.can regulate plant growth,the scientific and standardized use of phytohormones still remain problems.Hormone signals and light signals have a very complex interactive network.It is beneficial to improve the yield and quality of tomato by regulating endogenous hormones level by light quality.Studying the relationship between light quality and plant hormones can provide theoretical guidance for the regulation of tomato growth and development.In this paper,tomato was used as the research material to study the effects of red light(R)and low ratio red/far red light(L-R/FR)on the growth of tomato,investigate the interaction among long hypocotyl(HY5),gibberellin(GA)and brassinolide(BR),to study whether HY5 and BR induced gibberellin regulating leaf and stem elongation under low proportion of red light/far-red light.The main resu ts are as fo lows:1.Leaf and stem elongation induced by low proportion of red/far red light in tomato was related to gibberellin level.In this chapter,the growth rate of leaf and stem under L-R/FR was greater.L-R/FR induced gibberellin synthesis and metabolism relative gene expression in leaf and stem.L-R/FR promoted the accumulation of gibberellin in leaf.L-R/FR induced leaf and stem elongation was associated with the accumulation of gibberellin.Moreover.L-R/FR induced up-regulation of BR synthesis gene in leaf,but the BR content under L-R/FR was lower than red light.The HY5 gene responded to L-R/FR and was significantly unregulated at the transcriptional level,but its protein level was inhibited.In summary,light signals and GA,BR jointly regulated tomato growth and development,and they may have crosstalk.2.Gibberellin regulated leaf elongation in tomato under L-R/FR depending on the BR path.way,while stem elongation did not dependent on the BR pathway.Our researches have found that high level of BR inhibited GA synthesis and low level of BR promoted GA synthesis.Compared with the red light treatment,the stem elongation of four different endogenous BR level materials under L-R/FR treatment was equivalent.The increase of leaf area was most significant in DWF-OX2.while there were no significant changres in dtm and bzr1.Gibberellin regulated leaf elongation under L-R/FR depending on the BR pathway,while stem elongation is not dependent on the BR pathway.The results of GA hormone content indicated that endogenous BR enhanced the promotion of GA1 in leaf under L-R/FR and weakened the promoting effect of GA4 on stem under L-R/FR3.Gibberellin regulated leaf and stem elongation in tomato under L-R/FR depending on the degradation of HY5 protein.The study found that high concentration of endogenous BR did not significantly suppress HY5 protein accumulation.while low concentration of endogenous BR promoted HY5 protein accumulation.HY5 inhibited BR synthesis in stems.Compared with red light,the elongation of leaf and stem of 6 different HY5 level materials under L-R/FR treatment was most significant in hy5-RNAi and hy5-crispr materials.but the changes of OE-HY5-1,OE-HY5-1-2 were not remarkable,indicating that gibberellin regulated leaf and stem elongation under L-R/FR depending on the the degradation of HY5 protein.The GA hormone content data indicated that HY5 protein in leaf inhibited L-R/FR induced GA20 and GA3,and GAi and GA3 may involved in the promotion of leaf elongation.HY5 in stems inhibited the promotion of GA20 in stems under L-R/FR.and HY5 enhanced the inhibitory effect on GA3 under L-R/FR.GA1 may promotes stem elongation while GA3 inhibits stem elongation.