Deletion of a cyclin-dependent protein kinase inhibitor, CsSMR1, leads to dwarf and determinate growth in cucumber (Cucumis sativus L.)

Shuai Li,Xueyong Yang,Jie Wang,Jinjing Sun,Sanwen Huang,Huimin Zhang,Qiqi Zhang,Zhonghua Zhang

doi:10.1007/s00122-021-04006-7

Abstract

Key messageA 7.9 kb deletion which contains a cyclin-dependent protein kinase inhibitor leads to determinate growth and dwarf phenotype in cucumber.Plant architecture is a composite character which are mainly defined by shoot branching, internode elongation and shoot determinacy. Ideal architecture tends to increase the yield of plants, just like the case of “Green Revolution” increased by the application of semi-dwarf cereal crop varieties in 1960s. Cucumber (Cucumis sativus L.) is an important vegetable cultivated worldwide, and suitable architecture varieties were selected for different production systems. In this study, we obtained a novel dwarf mutant with strikingly shortened plant height and determinate growth habit. By bulked segregant analysis and map-based cloning, we delimited the dw2 locus to a 56.4 kb region which contain five genes. Among all the variations between WT and dw2 within the 56.4 kb region, a 7.9 kb deletion which resulted in complete deletion of CsaV3_5G035790 in dw2 was co-segregated with the dwarf phenotype. Haplotype analysis and gene expression analysis suggest that CsaV3_5G035790 encoding a cyclin-dependent protein kinase inhibitor (CsSMR1) be the candidate gene responsible for the dwarf phenotype in dw2. RNA-seq analysis shows that several kinesin-like proteins, cyclins and reported organ size regulators are expressed differentially between WT and dw2, which may account for the reduced organ size in dwarf plants. Additionally, the down-regulation of CsSTM and CsWOX9 in dw2 resulted in premature termination of shoot apical meristem development, which eventually reduces the internode number and plant height. Identification and characterization of the CsSMR1 provide a new insight into cucumber architecture modification to be applied to mechanized production system.

Highlights

Higher plants exhibit diverse architectures which are defined by the combination of shoot branching, internode elongation and shoot determinacy (Wang and Li 2008)
Identification of a novel dwarf mutant with determinate growth habit in cucumber Cucumber is one of the most popular vegetables all over the world, suitable plant architecture varieties are often selected for different production systems
Varieties with indeterminate growth habit are often grown under protected environments, for the fruits can be harvested continuously for an extended growth period; varieties with determinate growth habit and compact plant architecture are often selected under open fields, for it can be harvested once-over and planting with high-density

Summary

Introduction

Higher plants exhibit diverse architectures which are defined by the combination of shoot branching, internode elongation and shoot determinacy (Wang and Li 2008). There are many factors affecting internode elongation, while most of them involve in the plant hormone biosynthesis or signal transduction pathway. Based on extensive studies with mutants displayed dwarf phenotype, two plant hormones, gibberellin (GA) and brassinosteroid (BR), are regarded as major factors that determine plant height. GAs is a large family of tetracyclic diterpenoid plant hormones that play important roles in multiple plant growth and developmental processes, especially in stem elongation. The semidwarf rice results from a deficiency in the GA 20-oxidase

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Conclusion