High temperature is one of the most important environmental factors influencing rice growth, development, and yield. Therefore, it is important to understand how rice plants cope with high temperatures. Herein, the heat tolerances of T2 (Jinxibai) and T21 (Taizhongxianxuan2hao) were evaluated at 45 °C, and T21 was found to be sensitive to heat stress at the seedling stage. Analysis of the H₂O₂ and proline content revealed that the accumulation rate of H₂O₂ was higher in T21, whereas the accumulation rate of proline was higher in T2 after heat treatment. Meanwhile, transcriptome analysis revealed that several pathways participated in the heat response, including “protein processing in endoplasmic reticulum”, “plant hormone signal transduction”, and “carbon metabolism”. Additionally, our study also revealed that different pathways participate in heat stress responses upon prolonged stress. The pathway of “protein processing in endoplasmic reticulum” plays an important role in stress responses. We found that most genes involved in this pathway were upregulated and peaked at 0.5 or 1 h after heat treatment. Moreover, sixty transcription factors, including the members of the AP2/ERF, NAC, HSF, WRKY, and C2H2 families, were found to participate in the heat stress response. Many of them have also been reported to be involved in biotic or abiotic stresses. In addition, through PPI (protein–protein interactions) analysis, 22 genes were identified as key genes in the response to heat stress. This study improves our understanding of thermotolerance mechanisms in rice, and also lays a foundation for breeding thermotolerant cultivars via molecular breeding.

Short-term heat stress can affect the growth of rice (Oryza sativa L.) seedlings, subsequently decreasing yields. Determining the dynamic response of rice seedlings to short-term heat stress is highly important for accelerating research on rice heat tolerance. Here, we observed the seedling characteristics of two contrasting cultivars (T11: heat-tolerant and T15: heat-sensitive) after different durations of 42 °C heat stress. The dynamic transcriptomic changes of the two cultivars were monitored after 0 min, 10 min, 30 min, 1 h, 4 h, and 10 h of stress. The results indicate that several pathways were rapidly responding to heat stress, such as protein processing in the endoplasmic reticulum, glycerophospholipid metabolism, and plant hormone signal transduction. Functional annotation and cluster analysis of differentially expressed genes at different stress times indicate that the tolerant cultivar responded more rapidly and intensively to heat stress compared to the sensitive cultivar. The MAPK signaling pathway was found to be the specific early-response pathway of the tolerant cultivar. Moreover, by combining data from a GWAS and RNA-seq analysis, we identified 27 candidate genes. The reliability of the transcriptome data was verified using RT-qPCR on 10 candidate genes and 20 genes with different expression patterns. This study provides valuable information for short-term thermotolerance response mechanisms active at the rice seedling stage and lays a foundation for breeding thermotolerant varieties via molecular breeding.

Resistant starch (RS) shows several health benefits. Enhancing the RS content of wheat is of major commercial importance. However, knowledge regarding the RS synthesis mechanism in wheat remains limited. In this study, the dynamic accumulation of RS during the filling process in two wheat (Triticum aestivum L.) genotypes with contrasting RS contents (H242, high RS content; H189, low RS content) were investigated. The results demonstrate that beyond 25 days after pollination (DAP), the RS content of H189 was relatively stable, but that of H242 continued to increase. Secondary accumulation was observed in the high-RS-content wheat genotype. A comparative transcriptome analysis between H242 and H189 at 20 DAP and 35 DAP showed that the differentially expressed genes were mainly involved in glycerolipid metabolism, glycerophospholipid metabolism and glucuronate interconversions. Furthermore, weighted gene coexpression network analysis suggested that lipid metabolic pathways such as the glycerophospholipid metabolism pathway might be involved in RS synthesis, and lipid-related genes upregulated beyond 25 DAP resulted in RS secondary accumulation. This work provides insight into the characteristics and mechanisms of RS synthesis.

Cytokinins are key regulators of plant root development, but their dose-dependent effects on rice seedling roots and their physiological association with ethylene-related responses remain incompletely understood. In this study, rice seedlings were exposed to two exogenous cytokinins, 6-benzyladenine (6-BA) and kinetin (KT), at different concentrations for 3 and 6 d, and Ag⁺ was used as an inhibitor of ethylene action to evaluate its alleviating effect. Both 6-BA and KT significantly inhibited primary root elongation in a concentration- and time-dependent manner. At high cytokinin concentrations, primary root length was reduced by more than 60% relative to the control, accompanied by reductions in total root length, lateral root number, absorptive area, and root vigor, as well as increased MDA and ethylene levels. Ag⁺ partially alleviated cytokinin-induced primary root inhibition, with the strongest rescue effect observed near 0.08 μM. The recovery effect was particularly evident under moderate and high cytokinin concentrations. Correlation and principal component analyses further indicated that root morphological traits were negatively associated with MDA and ethylene but positively associated with root vigor. These results suggest that exogenous cytokinins restrict rice seedling root growth through a coordinated physiological response associated with ethylene accumulation and increased membrane lipid peroxidation, while Ag⁺ partially relieves this inhibition in association with mitigation of ethylene-related restriction. Because the study was based on short-term exogenous treatments and pharmacological inhibition, the findings should be interpreted as physiological evidence for ethylene-related involvement rather than direct proof of a complete signaling mechanism.