Agronomic, physiological and molecular characterisation of rice mutants revealed the key role of reactive oxygen species and catalase in high-temperature stress tolerance

Abstract

Climatic variations have increased the occurrence of heat stress during critical growth stages, which negatively affects grain yield in rice. Plants adapt to harsh environments, and particularly high-temperature stress, by regulating their physiological and biochemical processes, which are key tolerance mechanisms. The identification of heat-tolerant rice genotypes and reliable selection indices are crucial for rice improvement programs. Here, we evaluated the response of a rice mutant population for high-temperature stress at the seedling and reproductive stages based on agronomic, physiological and molecular indices. Estimates of variance components revealed significant differences (P < 0.001) among genotypes, treatments and their interactions for almost all traits. The principal component analysis showed significant diversity among genotypes and traits under high-temperature stress. The mutant HTT-121 was identified as the most heat-tolerant mutant with higher grain yield, panicle fertility, cell membrane thermo-stability (CMTS) and antioxidant enzyme levels under heat stress. Various seedling-based morpho-physiological traits (leaf fresh weight, relative water contents, malondialdehyde, CMTS) and biochemical traits (superoxide dismutase, catalase and hydrogen peroxide) explained variations in grain yield that could be used as selection indices for heat tolerance in rice during early growth. Notably, heat-sensitive mutants accumulated reactive oxygen species, reduced catalase activity and upregulated OsSRFP1 expression under heat stress, suggesting their key roles in regulating heat tolerance in rice. The heat-tolerant mutants identified in this study could be used in breeding programs and to develop mapping populations to unravel the underlying genetic architecture for heat-stress adaptability.

DPS1 regulates cuticle development and leaf senescence in rice

“…We further quantified the level of ROS and found a significantly higher ( p < 0.05) amount of H 2 O 2 in dps1 leaves (Figure 5c). We also measured the levels of malondialdehyde (MDA), which is a marker for ROS‐induced membrane lipid peroxidation (Zafar, Hameed, et al, 2020). A significantly higher ( p < 0.01) level of MDA was observed in dps1 leaves as compared with WT, suggesting ROS‐induced damage in dps1 (Figure 5d).…”

“…The equal amount of leaf tissues was immersed overnight in ethanol with gentle shaking. The absorbance of the extract was measured at 663 and 645 nm using a spectrophotometer (HITACHI, U2800) as described earlier (Zafar, Hameed, et al, 2020). Formulae for measurement of chlorophyll contents are here: Concentration of chlorophyll a (mg/g F.W) = (12.7*A663) ‐ (2.69*A645) Concentration of chlorophyll b (mg/g F.W) = (22.9*A645) ‐ (4.68*A663) …”

“…ROS was measured quantitatively in terms of H 2 O 2 from leaf extract of WT and dps1 plants, as described earlier (Zafar, Hameed, et al, 2020). Briefly, 100 mg of fresh leaf tissues was harvested and ground to a fine powder with liquid nitrogen.…”

“…S0038). The absorbance of the supernatant was measured at 560 nm, and H 2 O 2 was calculated using standard curve as reported earlier (Zafar, Hameed, et al, 2020).…”

Combined Transcriptome and Metabolome analysis of Pitaya fruit unveiled the mechanisms underlying Peel and pulp color formation

“…When the VIP ≥ 1, and fold change ≥2 or fold change ≤0.5, the metabolites were considered as differentially changed metabolites. Principal Component Analysis (PCA) was conducted as a multivariate statistical analysis to understand the variability among different groups of peel and pulp tissues [71]. Heatmaps with cluster analysis were constructed to show the pattern of gene expressions and separate the groups of genes with similar expression.…”