Study On The Mechanism Of SlBPC6 Regulating Tomato Plant Height

Tomato（Solanum lycopersicum）is a popular vegetable crop,and breeding high-quality varieties has long been the goal of researchers.Plant height is one of the most basic external characteristics of plants,and it is also a growth index for breeding high quality varieties.Dwarf phenotype has many advantages,such as improving plant resistance to external stress,promoting high density planting,increasing yield and benefiting mechanized harvesting.BASIC PENTACYSTEINE（BPC）is a type of plant-specific transcription factor,which plays an important role in regulating the growth and development of plants.However,there is no research on the function of tomato BPC family genes.In this research,the BPC family genes of tomato were identified,with emphasis on the verification of the transgenic function of the SlBPC6gene,and a series of molecular biology methods were used to analyze the molecular mechanism of its regulation of plant height.The research fingdings are as follows:1.Six BPC genes were identified in tomato genome.Phylogenetic tree analysis of tomato,Arabidopsis thaliana and rice revealed that all BPC proteins were classified into three groups.SlBPC2,SlBPC4 and SlBPC5 belonging to class I,SlBPC1 and SlBPC6 belonging to class II,and SlBPC3 belonging to class III.Subcellular localization experiment showed that the gene members of this family were located in the nucleus.2.Tomato BPC genes are expressed in all tissues.Class I members SlBPC2 and SlBPC4 and SlBPC5 are highly expressed in leaves and flowers,and Class II members SlBPC1 and SlBPC6 have higher expression levels in leaves,flowers and young fruits.Class III member SlBPC3 is most expressed in flowers and young fruits,but is low in leaves.3.Overexpression of SlBPC6 resulted in a decrease in plant height and a decrease in the content of endogenous active GA₁,GA₄and chlorophyll.The plant height of SlBPC6 CRISPR/Cas9 transgenic lines had no significant difference with background material at seedling stage,but it was significantly lower than the background material at late growth stage.GA₃sprayed with the SlBPC6overexpression transgenic lines,the plant height increased significantly and returned to the level of untreated background materials,indicating that SlBPC6 could respond to gibberellin.4.In the SlBPC6 overexpression transgenic lines,the relative expression of gibberellin synthesis pathway related genes SlKO,SlKAO,SlGA2ox3 and SlGA3ox2increased significantly,and the expression of SlGA20ox1 and SlGA20ox2 decreased significantly,suggesting that SlBPC6 may negatively regulate the expression of SlGA20ox1 and SlGA20ox2 or by positively regulating GA inactivation gene SlGA2ox3 to reduce the GA content in plants.5.There are multiple RGARAGRRA sequences（reported Arabidopsis BPC gene binding sequence）on the promoters of SlGA20ox1 and SlGA20ox2.Yeast one hybrid and dual luciferase assay showed that SlBPC6 can bind to the promoter of SlGA20ox1and SlGA20ox2,playing a role of transcriptional inhibition.Electrophoretic mobility shift assay further demonstrated that S1BPC6 protein can bind to the TGAGAGATA sequence on the promoter of SlGA20ox1 in vitro.6.The RNA-seq analysis of the young shoot tip tissue of the SlBPC6overexpression transgenic material found that compared with the control,there were1838 differentially expressed genes in the two groups.The KEGG pathway enrichment results showed that the differential genes were mainly enriched in metabolic pathways and biosynthesis of secondary metabolites.GO analysis showed that differential genes mainly mediate oxidation-reduction process,transcriptional regulation,biosynthesis and signal transduction of various plant hormones,stress response,photosynthesis and other biological processes.