Poaceae Orthologs of Rice OsSGL, DUF1645 Domain-Containing Genes, Positively Regulate Drought Tolerance, Grain Length and Weight in Rice

doi:10.1016/j.rsci.2021.11.001

Abstract

Abstract:

Grain yield is a polygenic trait that can be influenced by environmental factors and genetic compositions at all plant growth stages. Currently, the molecular mechanisms behind the coordination of the interaction between grain yield-related traits remain unknown. In this study, we characterized the function of four STRESS_tolerance and GRAIN_LENGTH (OsSGL) Poaceae ortholog genes that are transcribed into DUF1645 domain-containing proteins in relation to the grain length, grain weight, and drought stress-tolerance of rice. The transgenic plants with overexpressing or heterologous high levels of Poaceae OsSGL ortholog genes exhibited longer grain size than the wild type plants. Larger cells were seen in panicles of the four transgenic lines with paraffin sectioning and scanning electron microscopy analyses. In addition, four Poaceae OsSGL ortholog genes positively affected the drought tolerance of rice. Four transgenic plants displayed higher resistance to drought stress at the seedling and vegetative stages. RNA-sequencing and qRT-PCR results indicated that over- or heterologous-expression of four Poaceae OsSGL ortholog genes also affected the transcriptome of rice plants. These genes may play a role in auxin and cytokinin biosynthesis and their transduction pathways. Taken together, these results suggested that the four OsSGL orthologs have a conserved function in the regulation of stress-tolerance and cell growth by modulating hormonal biosynthesis and signaling.

Key words: graminaceous cereal crop, OsSGL gene, drought resistance, grain length, grain weight

Liu Kai, Li Minjuan, Zhang Bin, Yin Xuming, Xia Xinjie, Wang Manling, Cui Yanchun. Poaceae Orthologs of Rice OsSGL, DUF1645 Domain-Containing Genes, Positively Regulate Drought Tolerance, Grain Length and Weight in Rice[J]. Rice Science, 2022, 29(3): 257-267.

Figures/Tables 4

Fig. 1. Agronomic traits of mature plants, panicles and grains between wild type (WT) and transgenic rice lines. A-I, Gross morphology of WT and relevant transgenic plants (A-F), panicles (G), grains (H), and brown rice (I). Scale bars, 20 cm in A-F, 2 cm in G and 1 cm in H and I. L1 and L2 are two representative over-expression lines. J-L, Comparisons of plant height (J), grain length (K), and 1000-grain weight (L) between WT and transgenic rice lines. WT, indica rice cultivar KH2; OE-OsSGL, OsSGL over-expression lines; OE-SbSGL, SbSGL heterologous-expression lines; OE-ZmSGL, ZmSGL heterologous-expression lines; OE-SiSGL, SiSGL heterologous-expression lines; OE-OsSGL2, OsSGL2 over-expression lines. L1-L4, Over- or heterologous- expression rice lines 1 to 4 of T3 generation. All phenotypic data were measured from paddy-grown plants under normal cultivation conditions. Student’s t-test was used to generate the P values; Data are Mean ± SD (n = 3); *, P < 0.05, **, P < 0.01.

Fig. 2. Histological analysis of spikelet hulls of WT and four over- or heterologous- expression transgenic rice. A, Young spikelet hulls of WT and transgenic rice lines at 6 d before heading. The red line indicates the sites of the transverse sections. Scale bar, 2.5 mm. B-F, Transverse-section cut at the middle of spikelet hulls. Scale bars, 200 µm. G-K, Microscopic inspection inside and outside of spikelet hulls. The upper panels are magnification of indicated transverse- section area boxed in B-F. The bottom panels are scanning electron microscopy analysis of the outer surfaces of spikelet hulls. Scale bars, 20 and 150 µm, respectively. L, Comparison analysis of cell area in inner parenchyma layer shown in upper panels of G-K. M and N, Comparison analyses of cell length (M) and width (N) of outer epidermal cells shown in bottom panels of G-K. WT, indica rice cultivar KH2; OE-SbSGL, SbSGL heterologous-expression transgenic lines; OE-ZmSGL, ZmSGL heterologous- expression transgenic lines; OE-SiSGL, SiSGL heterologous-expression transgenic lines; OE-OsSGL2, OsSGL2 over-expression transgenic lines. Data are Mean ± SD (n = 3); Student’s t-test was used to generate the P values. *, P < 0.05; **, P < 0.01.

Fig. 3. OsSGL orthologs improve drought tolerance in rice. A, Phenotype comparison of WT and transgenic rice under drought treatment at 4-leaf seedling stage. B, Survival rate (ratio of surviving plants to total number of plants after re-watering) of WT and transgenic rice. Data are given as Mean ± SD (n = 3). Student’s t-test was used to generate the P values (**, P < 0.01). WT, Wild type, indica rice cultivar KH2; OE-OsSGL-L1/2, OsSGL over-expression lines; OE-SbSGL-L1/2, SbSGL heterologous-expression lines; OE-ZmSGL-L1/2, ZmSGL heterologous-expression lines; OE-SiSGL-L1/2, SiSGL heterologous-expression lines; OE-OsSGL2-L1/2, OsSGL2 over-expression lines.

Fig. 4. Genome-wide transcriptional profiles analyses for young inflorescence buds (1-2 cm in length) before heading in WT and four over- expression transgenic plants. A, Volcano plot analysis of differentially expressed genes (DEGs) in different comparisons. B and C, Analysis of DEGs with Venn diagram (B) and percentage chart (C). D, Heatmap of partial DEGs related to plant hormone signal transduction pathway. E, Gene Ontology enrichment. F, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment. WT, Wild type, indica rice cultivar KH2; OE-SbSGL, SbSGL heterologous- expression lines; OE-ZmSGL, ZmSGL heterologous-expression lines; OE-SiSGL, SiSGL heterologous-expression lines; OE-OsSGL2, OsSGL2 over-expression lines.

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