FLOURY ENDOSPERM20 encoding SHMT4 is required for rice endosperm development

• DOI: 10.1111/pbi.13858
• Publication Date: 2022-05-21T03:25:42Z
• Authors: Mengyuan Yan; Tian Pan; Yun Zhu; Xiaokang Jiang; Mingzhou Yu; Rongqi Wang; Feng Zhang; Sheng Luo; Xiuhao Bao; Yu Chen; Binglei Zhang; Ruonan Jing; Zhijun Cheng; Xin Zhang; Cailin Lei; Qibing Lin; Shanshan Zhu; Xiuping Guo; Yulong Ren; Jianmin Wan
• Keywords: 0301 basic medicine; 03 medical and health sciences; Gene Expression Regulation, Plant; Flour; Oryza; Starch; Brief Communication; Endosperm; Plant Proteins

Endosperm stores starch and proteins in cereal crop seeds, providing a major calorie source for human consumption. Rice, given its agricultural importance rich genetic resources, serves as model dissecting the molecular basis of endosperm development. Although many genes affecting development have been functionally characterized, our understanding storage substance accumulation remains fragmented (He et al., 2021; Huang 2021). Serine hydroxymethyltransferases (SHMTs) catalyse reversible conversion glycine to serine known organisms, including plants (Schirch Szebenyi, 2005). Genetic evidence from suggests involvement SHMTs biotic and/or abiotic stress responses (Liu 2012; Moreno 2005), but their potential functions remain obscure. To dissect mechanisms underlying development, we identified seven allelic floury mutants flo20-1 flo20-7 an ethylmethanesulfonate-mutagenized pool japonica rice variety Kitaake (Figure S1) chose in-depth studies. displayed defective evidenced by appearance ~23% reduction 1000-grain weight at maturity 1a,b). Starch protein contents were reduced lipid content was increased flo20-1, compared with wild type (WT; Figure 1b). investigate cytological disrupted accumulation, performed scanning electron microscopy (SEM) light endosperm. filled loosely arranged abnormal granules (SGs), tightly packed sharp-edged SGs WT 1c). Coomassie blue staining developing 10 days after flowering (DAF) revealed two types bodies (PBs): lightly stained PBIs densely PBIIs 1d). Notably, PBII morphology appeared be amorphous 1d), which is similar reported mutant altered composition (Ashida 2011). Floury grains reciprocal cross phenocopied S2), suggesting that FLO20 directly regulates Map-based cloning combined sequencing each flo20 harbours single-nucleotide substitution Os01g0874900, causing mis-sense, non-sense or splicing mutations (Figures 1e S3). We introduced genomic GFP-fused Os01g0874900 into calli generate transgenic complementation. As predicted, carrying either transgene translucent 1f), confirming represents FLO20-GFP functional. encodes predicted 64.8-kDa harbouring SHMT domain (https://www.uniprot.org/uniprot/Q8RYY6), named SHMT4. Immunoblotting using anti-SHMT4 antibodies detected SHMT4 all tissues examined. levels lower during early peaked ~12 DAF decreased thereafter 1g). SHMT4-GFP localized nuclei 1h). Given contains domain, determined whether loss affected enzymatic activity, found more than 64% activity abolished 1i). Unexpectedly, failed detect vitro 1j S4). usually function homozygous heterozygous complexes (Anderson Schirch anticipated, verified SHMT4's interacting itself homologues SHMT3&5 combination yeast two-hybrid (Y2H) well vivo biomolecular fluorescence complementation (BiFC) co-immunoprecipitation assays 1k–m S5). Using high-performance liquid chromatography, precipitate 1n), may cooperate other execute function. indeed SHMT3 alone 1o S6) mutation slightly significantly compromised activities SHMT4-GST 1p S7). Consistently, knockout exhibited 35.3% 64.1% although did not obviously affect 1i S8). Together, these results suggested works cooperatively such important SHMT3. specifically S-adenosyl-L-methionine synthetase SAMS2 mass spectrometry 1m), confirmed interaction via BiFC tobacco 1q). SAMSs methionine produce SAM, methylation donor transmethylation reactions intermediate polyamine ethylene biosynthesis (Li measured SAM concentrations endosperm, finding level threefold higher 1r). next bisulphite DNA determine affects genome-wide (Table S1). Compared WT, CG, CHG CHH methylations 1s, Table possible role methylation. Differentially methylated regions (DMRs) analysis 25 715 DMRs 15 888 differentially (DMGs) between S3, Data S1), included involved biosynthesis, transport Additionally, expression several transcript factor required 1t). causes changes probably through production. A leaky allele recently confer enhanced cadmium tolerance selenium uptake assimilation root shoot (Chen 2020). However, putative unclear. Here, Storage greatly determines nutritional functional qualities crops. noted caused disruption composition, value breeding special demands. study provided link plants. This work supported National Key R&D Program China (2021YFF1000200) Central Public-Interest Scientific Institution Basal Research Fund, (Y2021YJ18). The authors declare no conflict interest. J.M.W. Y.L.R supervised project. M.Y.Y, T.P., Y.L.R., Y.Z., X.K.J. M.Z.Y. experiments. Other technical supports; M.Y.Y prepared manuscript. S1 List S1-S8 Supplementary Figures. S1-S4 Tables. Please note: publisher responsible functionality any supporting information supplied authors. Any queries (other missing content) should directed corresponding author article.