Effects Of Low Temperature On Pedicel Abscission And Auxin Synthesis Key Genes Of Tomato

Tomato(Solanum lycopersicum L.)is one of the more widely cultivated thermophilic vegetables.It is often subjected to cold stress during the protected cultivation in northern of China,especially in the winter and spring season.Cold stress usually causes for tomato flowers droping and fail of fruits setting,which result in seriously affecting tomato yield.Auxin is one of the key phytohormones that affect the abscission of plant floral organs.The YUCCA(YUC)family is the key limiting enzyme in the auxin biosynthetic pathway.Although its function has been studied in Arabidopsis,it rarely has been reported in tomatoes.In this study,the bioinformatics method was used to analyze and identify the key gene family YUC/FZY in the tomato auxin biosynthesis pathway,and to perform subcellular localization and cis-acting element prediction analysis on the gene of this family;then use q RT-PCR technology,The expression patterns of FZY genes in different parts of tomato were analyzed,and the effect of genes expressed in the floral organs of tomato on the pedicel shedding was studied using VIGS technology;on this basis,the tomato was subjected to day and night low temperature and night low temperature stress treatment to determine the family The expression pattern under low temperature,and observe the pollen development,investigate the shedding rate and fruit setting rate,so as to verify whether the low temperature stress caused the tomato to drop flowers and fruits through regulating the auxin biosynthetic pathway.The main findings are as follows:Using bioinformatics analysis methods,members of the gene family encoding auxin synthesis were identified.On the tomato genome website,members of the FZY gene family that may encode flavin monooxygenase were found.Nine of them were found to contain the signature domain WL(I/V)VATGENAE between FAD and NADPH through DNAMAN,and three functional domains were located in motif5,7,2.Phylogenetic tree analysis showed that the tomato FZY family is closely related to the YUC family in Arabidopsis.The subcellular localization prediction of tomato FZY family found that 8 of them may be in the cytoplasm and the other one in the chloroplast.Analysis of promoter cis-acting elements revealed that all the members of this gene family in tomato contain photoresponsive elements,indicating that they are sensitive to light signals;only the promoters of Sl FZY4-2,Sl FZY5,Sl FZY7 contain low temperature response element.It is clear that the early stage of tomato pollen development is a key period in which low night temperature affects fruit setting rate.Through q RT-PCR analysis,it was found that the expression of Sl FZY2,3,4-1,5 was higher in floral organs.The highest expression level in the ground is Sl FZY3,the highest expression level of Sl FZY5 in stems and leaves,and the highest expression level of Sl FZY4-2 in young fruits.After low temperature treatment at the flower bud stage during the day and night,it was found that the low temperature treatment at 16/6℃ increased the shedding rate of tomato flower organs.The analysis of tomato seedlings with low temperature treatment at day and night and low temperature treatment at night showed that the expression level of auxin synthesis gene in stamen increased,while the expression level in pistil decreased,and pollen vigor and pollen germination rate were reduced.Low night temperature treatment of tomato reduced fruit setting rate and resulted in parthenogenesis.Low night temperature treatment during pollen development period reduced fruit setting rate significantly,and had little effect after pollen ripening after flowering.Using VIGS technology,it was clarified that Slfzy3 and Slfzy5 are the key genes that affect the shedding of tomato flower organs.Silencing of 4 genes such as Sl FZY2,3,4-1,5 with high expression levels of floral organs revealed that the stalk shedding rate of silent plants(p TRV-Slfzy2 and p TRV-Slfzy4)of tomato Slfzy2 and Slfzy4 was not significantly different from that of wild type The difference was that when Slfzy2,4(p TRV-Slfzy2,4)was silenced at the same time,the pedicel shedding rate was significantly higher than that of the control after 8 hours of de-flowering,indicating that the tomato FZY gene family function is redundant.The pedicel abscission rate of tomato Slfzy3 and Slfzy5(p TRV-Slfzy3 and p TRV-Slfzy5)silenced plants was extremely significantly higher than that of the control at 8h,and significantly higher than that of the control at 10 h,and all shedding was completed earlier than the control.After low-night temperature treatment at the early stage of tomato pollen development,the stamens at flowering stage were taken for high-throughput transcriptome sequencing.Under low night temperature treatment,there were 94 differential genes in tomato stamens,of which 8 were up-regulated and 84 were down-regulated.GO enrichment analysis found that 26 differential genes were enriched in the molecular functional part,7 in the cellular component part,and 27 in the biological process part.KEGG analysis found that there are three genes enriched in the plant hormone signal transduction pathway,namely Solyc07g043580,Solyc06g048600 and Solyc06g048930.These three genes were down-regulated after low temperature treatment at night.Two genes are enriched in the MAPK signaling pathway,namely Solyc06g005170 and Solyc09g014990,which encode Sl MAPK3 and Sl WRKY33,respectively,and the expression levels of these two genes are down-regulated.