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Title: A mutant in the CsDET2 gene leads to a systemic brassinosteriod deficiency and super compact phenotype in cucumber (Cucumis sativus L.)

Author
item HOU, SHANSHAN - Northwest Agricultural & Forestry University
item NIU, HUANHUAN - Northwest Agricultural & Forestry University
item TAO, QIANYI - Northwest Agricultural & Forestry University
item WANG, SHENHAO - Northwest Agricultural & Forestry University
item GONG, ZHENHUI - Northwest Agricultural & Forestry University
item LI, SEN - University Of Wisconsin
item Weng, Yiqun
item LI, ZHENG - Northwest Agricultural & Forestry University

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2017
Publication Date: 5/17/2017
Publication URL: http://handle.nal.usda.gov/10113/5746611
Citation: Hou, S., Niu, H., Tao, Q., Wang, S., Gong, Z., Li, S., Weng, Y., Li, Z. 2017. A mutant in the CsDET2 gene leads to a systemic brassinosteriod deficiency and super compact phenotype in cucumber (Cucumis sativus L.). Theoretical and Applied Genetics. 130(8):1693-1703. doi: 10.1007/s00122-017-2919-z.

Interpretive Summary: 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 it 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 a 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 5a-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 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.

Technical Abstract: The plant hormone brassinosteroids (BR) plays important roles in the development of plant architecture. Deficiecny of BR in plant may result in extreme dwarfism. Most cucumbers have an indeterminate growth habit, and dwarfism may have it 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 shows dark-green and 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 a 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 5a-reductase protein. Measurement of endogenous hormone levels indicated a reduced level of BR in the mutant, and the mutant phenotype could be partially rescued by the application of BR. 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.