A mutant in the CsDET2 gene leads to a systemic brassinosteriod deficiency and super compact phenotype in cucumber (Cucumis sativus L.)
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A novel dwarf cucumber mutant, scp-2, displays a typical BR biosynthesis-deficient phenotype, which is due to a mutation in CsDET2 for a steroid 5-alpha-reductase.
Brassinosteroids (BRs) are a group of plant hormones that play important roles in the development of plant architecture, and extreme dwarfism is a typical outcome of BR-deficiency. Most cucumber (Cucumis sativus L.) varieties have an indeterminate growth habit, and dwarfism may have its value in manipulation of plant architecture and improve production in certain production systems. In this study, we identified a spontaneous dwarf mutant, super compact-2 (scp-2), that also has dark green, wrinkle leaves. Genetic analyses indicated that scp-2 was different from two previously reported dwarf mutants: compact (cp) and super compact-1 (scp-1). Map-based cloning revealed that the mutant phenotype was due to two single nucleotide polymorphism and a single-base insertion in the CsDET2 gene that resulted in a missense mutation in a conserved amino acid and thus a truncated protein lacking the conserved catalytic domains in the predicted steroid 5α-reductase protein. Measurement of endogenous hormone levels indicated a reduced level of brassinolide (BL, a bioactive BR) in scp-2, and the mutant phenotype could be partially rescued by the application of epibrassinolide (EBR). In addition, scp-2 mutant seedlings exhibited dark-grown de-etiolation, and defects in cell elongation and vascular development. These data support that scp-2 is a BR biosynthesis-deficient mutant, and that the CsDET2 gene plays a key role in BR biosynthesis in cucumber. We also described the systemic BR responses and discussed the specific BR-related phenotypes in cucumber plants.
KeywordsGibberellic Acid Male Flower Dwarf Mutant Cucumber Chromosome Wrinkled Leaf
The authors thank Kristin Haider (USDA-ARS) for technical help and Professor Xiaofeng Wang (Northwest A&F University) for valuable suggestions on BR-related analysis. ZL and SL’s work in the University of Wisconsin at Madison visit was partially supported by the China Scholarship Council. This work was supported by the National Natural Science Foundation of China (Nos. 31471879, 31672150) (to ZL), the Innovation of Agricultural Science and Technology in Shaanxi Province (No. 2015NY081) (to ZL), the Young Talent Cultivation Project (Northwest A&F University) (to ZL) and the Agriculture and Food Research Initiative Competitive Grant 2013-67013-21105 from the U.S. Department of Agriculture National Institute of Food (to YW).
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Conflict of interest
The authors declare that they have no conflict of interest.
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