AUTHOR=Pan Yinghua , Chen Lei , Zhao Yan , Guo Haifeng , Li Jingcheng , Rashid Muhammad Abdul Rehman , Lu Chunju , Zhou Weiyong , Yang Xingka , Liang Yuntao , Wu Hao , Qing Dongjing , Gao Lijun , Dai Gaoxing , Li Danting , Deng Guofu 

TITLE=Natural Variation in OsMKK3 Contributes to Grain Size and Chalkiness in Rice

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.784037

DOI=10.3389/fpls.2021.784037

ISSN=1664-462X

ABSTRACT=<p>Rice (<italic>Oryza sativa</italic> L.) is an important staple food crop for more than half of the world’s population. Enhancing the grain quality and yield of rice to meet growing demand remains a major challenge. Here, we show that <italic>OsMKK3</italic> encode a MAP kinase kinase that controls grain size and chalkiness by affecting cell proliferation in spikelet hulls. We showed that <italic>OsSPL16</italic>, <italic>GS5</italic>, and <italic>GIF1</italic> have a substantial effect on the <italic>OsMKK3</italic>-regulated grain size pathway. <italic>OsMKK3</italic> has experienced strong directional selection in <italic>indica</italic> and <italic>japonica</italic>. Wild rice accessions contained four <italic>OsMKK3</italic> haplotypes, suggesting that the <italic>OsMKK3</italic> haplotypes present in cultivated rice likely originated from different wild rice accessions during rice domestication. <italic>OsMKK3</italic>-Hap1, <italic>gs3</italic>, and <italic>gw8</italic> were polymerized to enhance the grain length. Polymerization of beneficial alleles, such as <italic>OsMKK3</italic>-Hap1, <italic>gs3</italic>, <italic>gw8</italic>, <italic>fgr</italic>, <italic>alk</italic>, <italic>chalk5</italic>, and <italic>wx</italic>, also improved the quality of hybrid rice. Overall, the results indicated that beneficial <italic>OsMKK3</italic> alleles could be used for genomic-assisted breeding for rice cultivar improvement and be polymerized with other beneficial alleles.</p>