Zhengbin Tang, Xiuying Gao, Xiangyun Zhan, Nengyan Fang, Ruqin Wang, Chengfang Zhan, Jiaqi Zhang, Guang Cai, Jinping Cheng, Yongmei Bao, Hongsheng Zhang, Ji Huang

Plant Biotechnology Journal; 2021 Jan;19(1):14-16.  doi: 10.1111/pbi.13436.  

Identification of quantitative trait loci (QTLs) for grain length (GL) is important to rice breeding for increasing grain yield and appearance quality. Recent studies have identified a number of QTLs/genes as key grain length regulators by linkage mapping or genome‐wide association study (GWAS). These regulators are involved in G protein signalling, phytohormone signalling or transcriptional regulation, etc (Li et al., 2018). However, our current knowledge on GL is still fragmented in molecular mechanism and breeding utilization in rice. Here, we detected QTLs for GL by GWAS using 210 rice accessions from rice diversity panel 1 (RDP1) (McCouch et al., 2016) and linkage mapping using a recombinant inbred line (RIL) population with 116 lines derived from geng/japonica rice Suyunuo (long grain) and Bodao (short grain) (Figure 1a). Interestingly, one co‐localized locus was identified and LOC_Os06g15620 encoding a gibberellic acid‐stimulated regulator (GASR) protein included in this region was confirmed to control GL.

See https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7769224/

Figure 1:

Cloning and variation analysis of OsGASR7 for grain length in rice. (a) Grain morphology of Bodao (BD), Suyunuo (SYN) and some representative lines/accessions from RILs/RDP1. Scale bar, 5 mm. (b) Identification and positional cloning of OsGASR7 combining GWAS and linkage mapping. (b1) The genome‐wide association signals for grain length are shown in the region at about 8.5–10.0 Mb on chromosome 6 (x‐axis). Negative log10‐transformed P‐values from the EMMAX algorithm are plotted on the y‐axis. The position of the peak SNP is indicated by the red dot. The horizontal red line indicates the threshold (−log10(P) = 5.6). (b2) The QTL for grain length is shown in the region at 8.848–8.91 Mb on chromosome 6 (x‐axis). LOD values from ICIM‐ADD algorithm are plotted on the y‐axis. The horizontal red line is the LOD threshold (2.82). (b3) The physical position of the predicted ORFs (filled arrows). (b4) Non‐synonymous variants of OsGASR7 between Bodao and Suyunuo. Black lines represent introns, and colour bars represent exons. (c) OsGASR7 controls grain length. (c1, c2) Grain morphology of wild‐type Bodao (BD), Nipponbare (Nip) and transgenic complemental rice BD‐pOsGASR7^SYN::OsGASR7^SYN (B_CP), Nip‐pOsGASR7^SYN::OsGASR7^SYN (N_CP). Scale bar, 5 mm. (c3, c4) Statistical analysis of (brown) grain length of wild‐type plants and transgenic plants. The dashed lines and error lines represent means ± SD (n ≥ 4 plants, shown by dots). (c5) SEM observation of mature seeds. Scale bar, 1 mm for seed and 100 μm for lemma. (c6) Statistical analysis of cell length of the glume outer surfaces. Data are presented as means ± SD (n = 9). The P‐values are calculated by Student's t‐test. (d) InDel1 is significantly associated with grain length. (d1) The x‐axis indicates position of each variation in the ORF of OsGASR7 and the y‐axis is negative log10‐transformed P‐values from GLM algorithm. (d2) Six major genotypes of OsGASR7. (e) Genotype analysis of OsGASR7 for subpopulation distribution and grain length in 3K accessions (e1) and cultivars (e2). GJ: geng/japonica; XI: xian/indica; cA: centrum‐Aus; cB: centrum‐Basmati; BD: OsGASR7^BD; SYN: OsGASR7^SYN; I: OsGASR7^I;II: OsGASR7^II; III: OsGASR7^III; Ⅳ: OsGASR7^Ⅳ; nonSYN: cultivars without OsGASR7^SYN; number in brackets: number of statistical samples. Significance analysis is performed by Student's t‐test. (f) The subcellular localization of OsGASR7^BD‐GFP and OsGASR7^SYN‐GFP. Scale bar, 5 μm.