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The Cytochrome P450 Gene CsCYP85A1 Is a Putative Candidate for Super Compact-1 (Scp-1) Plant Architecture Mutation in Cucumber (Cucumis sativus L.)

Hui Wang, Wanqing Li, Yaguang Qin, Yupeng Pan, Xiaofeng Wang, Yiqun Weng, Peng Chen, Yuhong Li
Frontiers in plant science 2017 v.8 no.266 pp. -
Cucumis sativus, allelic variation, biosynthesis, brassinolide, chromosome mapping, crops, cucumbers, cytochrome P-450, exons, flowers, leaves, length, molecular cloning, mutants, mutation, phenotype, plant architecture, plant breeding, plant height, plant hormones, population, recessive genes, research, vines
The dwarf 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. We identified a super compact (SCP) mutant C257 which was extremely dwarf due to no internode elongation. Under dark growing condition, C257 did not show typical dark responses and the mutant phenotype could be rescued with exogenous application of brassinolide suggesting SCP might be a BR-deficient mutant. Segregation analysis revealed a single recessive gene scp-1 that was responsible for the SCP mutation. Map-based cloning identified CsCYP85A1, a member of the plant cytochrome P450 monooxygenase gene family, as the candidate gene for Scp-1, which encodes the BR-6-oxidase in the BR biosynthesis pathway. We show that a SNP within the second exon of Scp-1 candidate gene caused the SCP phenotype. Three copies of CsCYP85A gene exited in the cucumber genome, but only the Scp-1/CsCYP85A1 gene seemed active. The expression of CsCYP85A1 was higher in flowers than in the leaves and stem; its expression in the wild type was feedback regulated by brassinolide application. Its expression was reduced in C257 as compared with the wild type. 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 CsCYP85A1 in regulation of internode elongation in cucumber was discussed.