Nature variation in SPL-like transcription factor led to coordinated regulation of grain quality and yield in rice
Shaokui Wang¹, Kun Wu¹, Qingbo Yuan¹, Xueyuan Sun¹, Ruizhen Zeng², Haitao Zhu²,Guiquan Zhang²& Xiangdong Fu^1*

¹Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
²South China Agricultural University, Guangzhou, China
^*Corresponding Author: Xiangdong Fu, Tel/Fax: (+8610) 64806558; E-mail: xdfu@genetics.ac.cn

Abstract
Panicle size and grain shape are the important components of grain yield, and represent a character which has been much altered by human intervention since the species was first domesticated. Here we show that a quantitative trait locus GW8 is synonymous with OsSPL16, the product of which is a positive regulator of cell proliferation. Higher expression of this gene promotes cell division and grain filling, with positive consequences for grain width and yield in rice. Conversely, the downregulation of this gene results in the formation of a more slender grain. The correlation between grain size and allelic variation at the GW8 locus suggests that mutations within the promoter region were selected in rice breeding programs:the Basmati gw8 allele was retained because of its association with better grain quality, while the elite indica variety GW8 allele enhances grain yield. Interestingly, a loss-of-function OsSPL16 mutant developed higher grain numbers, whereas the transgenic wild-type plants overexpressing OsSPL16 developed less panicle branches. These results suggested that OsSPL16 functions as a negative regulator of panicle branching. We also demonstrate that the use of a marker-assisted strategy targeted at elite alleles of GW8 and GS3 genes underlying grain size can be effective in simultaneously improving grain quality and yield.

Key Words: GW8; panicle branching; grain shape; rice