Rice gene, OsCKX2-2 , regulates inflorescence and grain size by increasing endogenous cytokinin content
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ORIGINAL PAPER
Rice gene, OsCKX2-2, regulates inflorescence and grain size by increasing endogenous cytokinin content Yohannes Tsago1,2 · Ziyan Chen1 · Huan Cao1 · Mustapha Sunusi1 · Asad Ullah Khan1 · Chunhai Shi1 · Xiaoli Jin1 Received: 1 November 2019 / Accepted: 12 June 2020 © Springer Nature B.V. 2020
Abstract Panicle size is one of the yield determining traits in rice (Oryza sativa L.). In the current study, a rice mutant named cytokinin oxidase/dehydrogenase (Osckx2-2) was developed from the indica cultivar 9311 by ethyl methanesulfonate (EMS) mutagenesis. A comparison of agronomic traits showed that the panicle of the Osckx2-2 mutant was longer with dense branching pattern and higher seed setting rate compared to the wild-type (WT). In addition, the grains in the Osckx2-2 mutant were markedly longer, wider, and heavier compared to the WT. Histological analysis revealed that a higher number of the spikelet cells with bigger size resulted in larger grains in the Osckx2-2 mutant. By map-based cloning, SNP was detected in the 3′-UTR of the OsCKX2-2 gene which encodes cytokinin dehydrogenase and the cleaved amplified polymorphic sequence (CAPS) marker was developed based on the detected SNP. The RT-qPCR analysis displayed a decreased OsCKX2-2 expression in the Osckx2-2 mutant panicles. Meanwhile, the enzymatic activity assay showed the reduced cytokinin dehydrogenase enzyme activity, whereas the enzyme-linked immunosorbent assay (ELISA) revealed remarkably higher endogenous cytokinin content in the Osckx2-2 mutant in contrast to WT. The analysis of grain quality parameters showed that the degree of chalkiness and gel consistency decreased, while the amylose content and alkaline spreading value increased in the Osckx2-2 mutant. The OsCKX2-2 gene and Osckx2-2 mutant would be beneficial in marker-assisted backcrossing to improve yield in rice. Keywords Gene mapping · Phenotypic analysis · Panicle size · Grain quality · Rice Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10725-020-00637-w) contains supplementary material, which is available to authorized users. * Xiaoli Jin [email protected] Yohannes Tsago [email protected] Ziyan Chen [email protected] Huan Cao [email protected] Mustapha Sunusi [email protected] Asad Ullah Khan [email protected] Chunhai Shi [email protected] 1
Department of Agronomy, The Key Laboratory of Crop Germplasm Resource of Zhejiang Province, Zhejiang University, Hangzhou 310058, Zhejiang, China
Department of Biology, Madda Walabu University, Bale Robe, Ethiopia
2
Introduction Rice (Oryza sativa L.) is one of the staple food crops in the world after maize and wheat. Genetic improvements through identification of semi-dwarf genes and development of hybrids increased yield of rice from 2.29 to 7.75 tons/ha in the past 50 years (Huang et al. 2011; Zhang et al. 2009). Increasing the yield beyond 10 tons/ha is required to meet the demand driven by the increasing human population and decreasing cultivated land (X
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