Increased ATPase activity promotes heat-resistance, high-yield, and high-quality traits in rice by improving energy status

Acetate prevents pistil dysfunction in rice under heat stress by inducing methyl jasmonate and quercetin synthesis

INTRODUCTION

Acetic acid (HAC) is a crucial signal molecule in plant stress responses; however, its role in conferring heat tolerance to rice remains unclear.

OBJECTIVES

This study aims to investigate the effect of HAC in protecting pistil function under heat stress and its potential role in facilitating pollen germination and tube growth via HAC-induced synthesis of methyl jasmonate (MeJA) and quercetin (QR).

METHODS

Physiological analysis, including pollen germination, pollen tube growth into the ovule, reactive oxygen species (ROS), as well as the levels of HAC, acetyl coenzyme A (acetyl-CoA), MeJA, and QR in the pistils of heat stress-treated early indica rice cultivars Zhongzao39 (ZZ39) and Zhongjiazao17 (ZJZ17), were conducted. RNA sequencing (RNA-seq) was performed to identify differentially expressed genes involved in this process. Effect of exogenous acetate (NaAC), MeJA, and QR on spikelet fertility were also investigated.

RESULTS

Compared with ZJZ17, severe inhibition of spikelet fertility, pollen germination, and pollen tube growth was observed in ZZ39, due to the ROS burst and an irregular distribution across the stigma, style, and ovule. RNA-seq and physiological data indicate that HAC may activate acetyl-CoA to enhance heat tolerance by inducing the synthesis of MeJA and QR. Exogenous NaAC enhanced spikelet fertility under heat stress, accompanied by elevated antioxidant enzyme activities, improved energy status, and increased levels of acetyl-CoA, MeJA, and QR in the pistils. Additionally, NaAC, MeJA, and QR, either alone or in combination, effectively augmented spikelet fertility under heat stress, while the combination of MeJA and QR inhibitors significantly reduced fertility.

CONCLUSION

Acetate activates acetyl-CoA to induce the synthesis of both MeJA and QR, thereby alleviating heat-induced pistil dysfunction by maintaining ROS homeostasis and enhancing the pollen germination, pollen tube growth and spikelet fertility. Our results offer a promising strategy to enhance the heat tolerance of crops.

Increased Photosynthetic Capacity and Energy Status Contribute to Higher Grain Yield in Early Rice

As the economy develops and urbanization progresses, the amount of arable land continues to decline. In this context, the cultivation of double-season rice is particularly important for enhancing yield per unit area. However, research on the physiological mechanisms that contribute to high yields in double-season early rice varieties with short growing seasons is still limited. To address this gap, we conducted a field study using two early rice varieties, Zhongzu18 and Yongxian15, to examine their production characteristics, photosynthesis, fluorescence, and energy metabolism. The results indicate that Zhongzu18 has a significantly higher seed-setting rate, grain weight, and total grain yield compared to Yongxian15. Additionally, Zhongzu18 exhibits a higher head rice rate and a lower degree of chalkiness, along with a reduced chalky grain rate. Furthermore, the total dry matter weight and the ratio of panicle weight to total weight for Zhongzu18 were significantly greater than those for Yongxian15. After anthesis, Zhongzu18 also demonstrated a higher leaf net photosynthetic rate and actual fluorescence quantum efficiency compared to Yongxian15. Moreover, the levels of ATP and ATPase, as well as the activities of antioxidant enzymes and the expression of sucrose transport-related genes, were significantly increased in Zhongzu18 plants relative to Yongxian15. We conclude that the enhanced photosynthetic efficiency and energy production in Zhongzu18 lead to more effective assimilation and carbohydrate transport to the grains, resulting in higher grain yields and improved rice quality.

GRAIN SIZE ON CHROMOSOME 2 orchestrates phytohormone, sugar signaling and energy metabolism to confer thermal resistance in rice

GRAIN SIZE ON CHROMOSOME 2 (GS2) has been reported to enhance rice grain yield and confer tolerance to cold, drought, and salt stress, but its function in heat tolerance of rice remains undocumented. This study aimed to investigate whether GS2 could enhance thermal tolerance by subjecting rice seedlings of Huazhan (HZ) and its near-isogenic line (HZ-GS2) to heat stress. HZ-GS2 plants exhibited less damage compared to HZ plants under heat stress. Transcriptome revealed the involvement of phytohormones, sugar signaling, and energy metabolism in the mechanism by which GS2 influences heat tolerance. Under heat stress, HZ-GS2 plants showed higher increases or lower decreases in glucose, gibberellins (GAs), salicylic acid (SA), indoleacetic acid (IAA), adenosine triphosphate (ATP), energy charge, as well as the activities of hexokinase, NADH dehydrogenase, cytochrome oxidase, ATP synthase, and ATPase. Exogenous GA3 enhanced heat tolerance in rice by increasing energy charge, ATPase, activities of complex V and hexokinase. Additionally, glucose, sucrose, 3-aminobenzamide (3-ab), and Na2SO3 conferred heat tolerance in rice plants. Importantly, a significant increase in Fv/Fm was observed in plants treated with a combination of GA3, glucose, and 3-ab, compared to those sprayed alone. Thus, GS2 coordinates GA3, hexokinase, and energy metabolism to improve energy status, thereby enhancing heat tolerance in rice plants.

Effects of Heat Stress on Plant-Nutrient Relations: An Update on Nutrient Uptake, Transport, and Assimilation

As a consequence of global climate change, the frequency, severity, and duration of heat stress are increasing, impacting plant growth, development, and reproduction. While several studies have focused on the physiological and molecular aspects of heat stress, there is growing concern that crop quality, particularly nutritional content and phytochemicals important for human health, is also negatively impacted. This comprehensive review aims to provide profound insights into the multifaceted effects of heat stress on plant-nutrient relationships, with a particular emphasis on tissue nutrient concentration, the pivotal nutrient-uptake proteins unique to both macro- and micronutrients, and the effects on dietary phytochemicals. Finally, we propose a new approach to investigate the response of plants to heat stress by exploring the possible role of plant peroxisomes in the context of heat stress and nutrient mobilization. Understanding these complex mechanisms is crucial for developing strategies to improve plant nutrition and resilience during heat stress.

RGA1 Negatively Regulates Thermo-tolerance by Affecting Carbohydrate Metabolism and the Energy Supply in Rice

BACKGROUND

Signal transduction mediated by heterotrimeric G proteins, which comprise the α, β, and γ subunits, is one of the most important signaling pathways in rice plants. RGA1, which encodes the Gα subunit of the G protein, plays an important role in the response to various types of abiotic stress, including salt, drought, and cold stress. However, the role of RGA1 in the response to heat stress remains unclear.

RESULTS

The heat-resistant mutant ett1 (enhanced thermo-tolerance 1) with a new allele of the RGA1 gene was derived from an ethane methyl sulfonate-induced Zhonghua11 mutant. After 45 °C heat stress treatment for 36 h and recovery for 7 d, the survival rate of the ett1 mutants was significantly higher than that of wild-type (WT) plants. The malondialdehyde content was lower, and the maximum fluorescence quantum yield of photosystem II, peroxidase activity, and hsp expression were higher in ett1 mutants than in WT plants after 12 h of exposure to 45 °C. The RNA-sequencing results revealed that the expression of genes involved in the metabolism of carbohydrate, nicotinamide adenine dinucleotide, and energy was up-regulated in ett1 under heat stress. The carbohydrate content and the relative expression of genes involved in sucrose metabolism indicated that carbohydrate metabolism was accelerated in ett1 under heat stress. Energy parameters, including the adenosine triphosphate (ATP) content and the energy charge, were significantly higher in the ett1 mutants than in WT plants under heat stress. Importantly, exogenous glucose can alleviate the damages on rice seedling plants caused by heat stress.

CONCLUSION

RGA1 negatively regulates the thermo-tolerance in rice seedling plants through affecting carbohydrate and energy metabolism.

Oligomeric Proanthocyanidins Confer Cold Tolerance in Rice through Maintaining Energy Homeostasis

Oligomeric proanthocyanidins (OPCs) are abundant polyphenols found in foods and botanicals that benefit human health, but our understanding of the functions of OPCs in rice plants is limited, particularly under cold stress. Two rice genotypes, named Zhongzao39 (ZZ39) and its recombinant inbred line RIL82, were subjected to cold stress. More damage was caused to RIL82 by cold stress than to ZZ39 plants. Transcriptome analysis suggested that OPCs were involved in regulating cold tolerance in the two genotypes. A greater increase in OPCs content was detected in ZZ39 than in RIL82 plants under cold stress compared to their respective controls. Exogenous OPCs alleviated cold damage of rice plants by increasing antioxidant capacity. ATPase activity was higher and poly (ADP-ribose) polymerase (PARP) activity was lower under cold stress in ZZ39 than in RIL82 plants. Importantly, improvements in cold tolerance were observed in plants treated with the OPCs and 3-aminobenzamide (PARP inhibitor, 3ab) combination compared to the seedling plants treated with H₂O, OPCs, or 3ab alone. Therefore, OPCs increased ATPase activity and inhibited PARP activity to provide sufficient energy for rice seedling plants to develop antioxidant capacity against cold stress.