The Elite Alleles of OsSPL4 Regulate Grain Size and Increase Grain Yield in Rice

Jihong Hu,Yesheng Zhang,Wen Wang,Shilai Zhang,Ru Zhang,Qingyi Hu,Guanglong Chen,Hui Liu,Jintao Liu,Fengyi Hu,Liyu Huang,Yi Ding

doi:10.1186/s12284-021-00531-7

Abstract

Grain weight and grain number, the two important yield traits, are mainly determined by grain size and panicle architecture in rice. Herein, we report the identification and functional analysis of OsSPL4 in panicle and grain development of rice. Using CRISPR/Cas9 system, two elite alleles of OsSPL4 were obtained, which exhibited an increasing number of grains per panicle and grain size, resulting in increase of rice yield. Cytological analysis showed that OsSPL4 could regulate spikelet development by promoting cell division. The results of RNA-seq and qRT-PCR validations also demonstrated that several MADS-box and cell-cycle genes were up-regulated in the mutation lines. Co-expression network revealed that many yield-related genes were involved in the regulation network of OsSPL4. In addition, OsSPL4 could be cleaved by the osa-miR156 in vivo, and the OsmiR156-OsSPL4 module might regulate the grain size in rice. Further analysis indicated that the large-grain allele of OsSPL4 in indica rice might introgress from aus varieties under artificial selection. Taken together, our findings suggested that OsSPL4 could be as a key regulator of grain size by acting on cell division control and provided a strategy for panicle architecture and grain size modification for yield improvement in rice.

Highlights

Rice (Oryza sativa L.) is a staple food for more than half of the world’s population
Two homozygous mutation of OsSPL4 with depressed activity could increase grain length and width as well as grain yield, these deletions not cause any other changes in amino acid sequences (Fig. 3, Fig. 6E, Additional file 1: Fig. S1).To further investigate the function of OsSPL4 in rice, we successfully generated transgenic plants overexpressing OsSPL4 in Nipponbare background
Mutation of OsSPL4 in rice increased the number of grains per panicle and grain size based on the results of phenotyping, cytological observation, dual-luciferase assays, and RNA-seq analysis

Summary

Introduction

Rice (Oryza sativa L.) is a staple food for more than half of the world’s population. Increasing grain yield is a longterm goal for crop breeding to meet the demand of global food security. At the individual plant level, rice grain yield is determined by three component traits: number of tillers (panicles) per plant, number of grains per panicle, and grain weight (Mao et al 2010). In the past years, many genes and quantitative trait loci (QTLs) controlling panicle architecture and grain size have been cloned and characterized (Bai et al 2012; Zou and Li, 2014; Li et al 2019). Several genes, including DEP1, GS3, GL3.1, GL7, GL3.3/TGW3 and OsGRF4, have been reported to regulate grain length through coordinating alternation of cell division and expansion

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