Montoya et al. cloned the gene responsible for the tomato plant mutant altered brassinolide sensitivity 1 (abs1). This gene was an allele to the curl3 (cu3) gene. Plants with mutations in cu3 do not respond to brassinolide steroid hormones and have increased concentrations of brassinolides, which together suggest loss of negative feedback. Identification of the tomato homolog of the Arabidopsis brassinolide receptor BR1, a leucine-rich repeat receptor-like kinase, and subsequent comparison of the tBR1 sequences from wild-type and curl3 plants showed that cu3 encoded a nonsense mutation. tBR1 is essentially identical to the putative systemin receptor SR160. Systemin is a peptide important for defense signaling in plants. Thus, steroid hormones and peptides may share a common receptor, which raises intriguing questions about the interaction between brassinolide signaling (involved in growth and development) and defense signaling (involved in plant immune responses to pathogen attack).
T. Montoya, T. Nomura, K. Farrar, T. Kaneta, T. Yokota, G. J. Bishop, Cloning the tomato Curl3 gene highlights the putative dual role of the leucine-rich repeat receptor kinase tBRI1/SR160 in plant steroid hormone and peptide hormone signaling. Plant Cell 14, 3163-3176 (2002). [Abstract] [Full Text]