The Role Of Tomato Cryptochrome 1a In The Regulation Of Plant Growth And Development

Cryptochromes are blue light receptors,and play important role in plant growth and development.However,majority of the studies concerning the role of CRYs in plant growth and development were focused on he early growth stage and little information is available on the advanced growth stage of plant life cycle.In an attempt to functionally characterize the tomato CRY1a,we performed experiments by using both tomato cryla mutants(loss-of-function)and CRY1a-overexpressing lines(OE-CRY1a-1 and OE-CRY1a-2),together with the WT plants.The main results are as follows:1.The role of CRY1a in phytohormone homeostasis and plant development.In this study,we found that in comparison with wild-type plants,cry1a mutants are relatively tall and accumulate low biomass,whereas OE-CRY1a plants are short stature with thick leaves,and also accumulate low biomass.RNA-seq,qRT-PCR and LC-MS/MS analysis revealed that biosynthesis of gibberellin,cytokinin and jasmonic acid was down-regulated by CRY1a.Furthermore,DNA replication was drastically inhibited in leaves of OE-CRY1a lines,but promoted in cryla mutants with concomitant changes in the expression of cell cycle genes.The results indicate the important role of CRY1a in plant growth.2.CRY1a significantly promoted the growth of lateral branch via affecting the phytohormone homeostasis of auxin(e.g.indole-3-acetic acid;IAA),cytokinins(CTKs)and strigolactones(SLs)in tomato plants.CRY1a surpressed the biosynthesis of IAA in the terminal bud,hence abolished the apical dominance.CRY1a also surpressed the biosynthesis of strigolactones in roots,wheares promoted the accumulation of cytokinins in the nodes,which resulted in decreased ratio between IAA and CTKs,accompanied by down-regulation of the transcription of BRC1.These results deepened our understanding of the regulatory mechanism of CRY1a-mediated lateral branching development.3.Molecular mechanism of CRY1a-induced anthocyanin biosynthesis in tomato.We found that exposure to blue light and overexpression of CRY1a are associated with increased accumulation of anthocyanin in tomato(Solarium lycopersicum L.).These responses are the result of changes in mRNA and the protein levels of SIHY5.In vitro and in vivo experiments using EMSA and ChIP-qPCR assays revealed that SlHY5,a transcription factor,could directly recognize and bind to the G-box and ACE motifs in the promoters of anthocyanin biosynthesis genes,such as CHS1,CHS2 and DFR.Furthermore,silencing of SlHY5 in OE-CRY1a lines decreased the accumulation of anthocyanin.These findings presented here not only deepened our understanding of how light controls anthocyanin biosynthesis and associated photoprotection in tomato leaves,but also allowed us to explore potential targets for improving pigment production.4.Effect of CRY1a on the flowering time,fruit productivity and quality.Overexpression of CRY1a resulted in delayed flowering time,decreased fruit weight and yield per plant.However,analysis of the phytonutrients showed that overexpression of CRY1a positively regulate the accumulation of glucose,fructose,citric acid and lycopene,while decreased the accumulation of sucrose and malic acid in ripen fruits.These results suggest that although CRYla negatively regulate the yield of fruits,it significantly promote the accumulation of phytonutrients,which were beneficial to human health.