The Cytochrome P450 Gene Is a Putative Candidate for () Plant Architecture Mutation in Cucumber ( L.).

The dwarf or compact plant architecture is an important trait in plant breeding. A number of genes controlling plant height have been cloned and functionally characterized which often involve in biosynthesis or signaling of plant hormones such as brassinosteroids (BRs). No genes for plant height or vine length have been cloned in cucurbit crops (family ). From an EMS-induced mutagenesis population, we identified a (SCP) mutant C257 which was extremely dwarf due to practically no internode elongation. Under dark growing condition, C257 did not undergo skotomorphogenesis and its mutant phenotype could be rescued with exogenous application of brassinolide (BL), suggesting SCP might be a BR-deficient mutant. Segregation analysis revealed a single recessive gene that was responsible for the SCP mutation. Map-based cloning combined with a modified MutMap identified , a member of the plant cytochrome P450 monooxygenase gene family, as the most possible candidate gene for , which encodes a BR-C6-oxidase in the BR biosynthesis pathway. We show that a SNP within the second exon of candidate gene caused the SCP phenotype. Three copies of the gene are present in the cucumber genome, but only the / gene seemed active. The expression of was higher in flowers than in the leaves and stem; its expression in the wild type (WT) was feedback regulated by BL application. Its expression was reduced in C257 as compared with the WT. This was the first report of map-based cloning of a plant height gene in cucurbit crops. The research highlighted the combined use of linkage mapping, an improved MutMap method and allelic diversity analysis in natural populations in quick cloning of simply inherited genes in cucumber. The roles of in regulation of internode elongation in cucumber was discussed.