Favorable allele mining and breeding utilization of ALK in rice

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Favorable allele mining and breeding utilization of ALK in rice Ling Zheng & Pin Liu & Shangxing Zhang & Jialian Li & Yaseen Muhammad & Yifan Yun & Li Hu & Fengying Xue & Yangkai Wang & Hua Yuan & Weilan Chen & Peng Qin & Bingtian Ma & Shigui Li & Bin Tu & Yuping Wang

Received: 20 August 2020 / Accepted: 26 October 2020 / Published online: 18 November 2020 # Springer Nature B.V. 2020

Abstract ALK is the key gene of controlling rice gelatinization temperature (GT), and at least three ALK alleles are thought to be responsible for the diversity of GT among rice cultivars. But whether the sequence polymorphism of the promoter region

Ling Zheng, Pin Liu and Shangxing Zhang contributed equally to this work. Main conclusion Based on the functional analysis of sequence variation in ALK promoters and the verification of favorable allele, in combination with the study of gene expression pattern in endosperm and the development of molecular markers, we proposed a strategy for improving the alkali value of hybrid rice. L. Zheng : P. Liu : J. Li : Y. Muhammad : Y. Yun : L. Hu : F. Xue : Y. Wang : W. Chen : P. Qin : B. Ma : S. Li : B. Tu (*) : Y. Wang (*) Rice Research Institute, Sichuan Agricultural University, Wenjiang, Chengdu, Sichuan 611130, People’s Republic of China e-mail: [email protected] e-mail: [email protected] L. Zheng Hybrid Rice Research Center of Neijiang Academy of Agricultural, Neijiang, Sichuan 641000, People’s Republic of China S. Zhang Zunyi Agricultural Science Research Institute, Zunyi, Guizhou 563000, People’s Republic of China H. Yuan : P. Qin : S. Li : B. Tu State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Wenjiang, Chengdu, Sichuan 611130, People’s Republic of China

also associated with GT is not clearly studied. In this study, we analyzed sequence variation in the promoter region of ALK and mainly two types of promoter were identified. ALK type I promoter prevails among thousands of indica and japonica rice varieties, while ALK type II promoter predominates over varieties from Aus/boro and Basmati ecotypes. Phenotypic analysis and quality characterization of CSSLs with different alleles of ALK and promoter activity assays revealed that type II promoter downregulates the expression level of ALK and subsequently, negatively affects ASV values. ALKQ1882, owning type II promoter region and TT SNP at 4329/4330 bp of ALK gene, was identified as a rare and elite ALK allele for rice quality improvement. Transcriptional detection in hybrid triploid endosperm revealed that ALK is simultaneously expressed by gene copes from both parents, the ASV of hybrid rice varieties can be estimated through the genotypes of two parents. More importantly, a new dCAPS marker was developed to discriminate the functional SNP of TT at 4329/4330 bp, which is an efficient tool for improving the grain quality with high accuracy on low testing cost.

Keywords Rice . Gelatinization temperature . ALK gene . Sequence polymorphism . dCAPS marker

Mol Breeding (2020) 40: 107