Identification and Characterization of Brassinosteroid Biosynthesis and Signaling Pathway Genes in Solanum tuberosum.

Brassinosteroids (BRs) are plant hormones which promote plant growth and development. Their biosynthetic pathway and signal transduction pathway have been well studied in Arabidopsis thaliana and rice. However, their pathways in Solanaceae plants, especially in potato are still elusive. For now, only several candidate genes have been reported by transcriptome sequencing or homologous clones, but there is little information on their characteristics and functions in tuberization and heat defense. In this study, we systematically identified a series of putative homologs of BRs synthesis and signaling genes in potato (Solanum tuberosum L.) cv. Désirée through bioinformatic and molecular technologies, named as StCPD, StDWF4, StDWARF, StDET2, StBRI1, StBIN2, StBZR1-2 and StBZR1-4. Exogenous BR treatment decreased the expression of all synthesis genes and signaling genes except the negative signal gene StBIN2 which was increased, demonstrating that there exists a feedback regulation for all these genes. Tissue expression analysis revealed that the majority of these genes were highly expressed in leaves, and only the downstream transcription factor gene StBZR1-2 was highly expressed in stolons and tubers. The expression of these genes after heat treatment showed the opposite results from BRs treatment, suggesting that BRs signaling can be activated by heat stress. Furthermore, we explored the effects of BRs on tuber formation and found that exogenous BRs application increased both the number and the total weight of potato tuber due to the activated light-period signal for tuberization. All these results indicated that BRs play an important role in potato tuberization and heat stress defense. [ABSTRACT FROM AUTHOR]