Response of brassinosteroids to nitrogen rates and their regulation on rice spikelet degeneration during meiosis

Abstract

The plant steroid hormones brassinosteroids (BRs) play pivotal roles in modulating flower and fruit production. Nitrogen (N) is a key factor affecting rice (Oryza sativa L.) production. We hypothesized that BRs would respond to N application rates at spikelet differentiation (SD) and regulate spikelet degeneration in rice. Three rice cultivars were field‐grown and treated with five N rates at SD. Plant N and BRs contents, antioxidant capacity, and energy status were observed during meiosis in young panicles, and their relationships with spikelet degeneration were evaluated. In all the N treatments, the BRs, adenosine triphosphate, and energy charge levels, activities of the enzymes involved in energy metabolism, including cytochrome C oxidase and succinate dehydrogenase, total antioxidant capacity, and grain yield, were the highest, whereas hydrogen peroxide (H2O2) content and vacuolar processing enzymes (VPE) genes expression levels, and spikelet degeneration rate were the lowest when plant N content was 2.6% during meiosis. The rice BRs‐deficient mutants showed substantial reduction in BRs levels, antioxidant capacity, and energy status, but great increase in H2O2 content, VPE genes expression levels, and spikelet degeneration rate than the wild type (WT); moreover, these parameters in WT panicles could be regulated, whereas in BRs‐deficient mutant panicles, they were not distinctly affected by N application. The results indicated that BRs mediate the effects of N rates on spikelet degeneration, and elevated BRs levels in rice panicles effectively inhibit spikelet degeneration when plant N content is 2.6% during meiosis by elevating antioxidant capacity and energy status.

Nitrogen forms and irrigation regimes interact to affect rice yield by regulating the source and sink characteristics

“…The effects of nitrogen‐application rates and irrigation methods on grain yield vary with rice genotype (Wang, Zhang, et al., 2016; Xu, Giu, et al., 2019; Zhang et al., 2020). In the present study, only the japonica rice Xudao3 was investigated under nitrogen forms and alternate wetting and drying irrigation, and further research is still needed to verify such an interaction by using more rice cultivars to understand the underlying mechanism.…”

Amino Acids in Rice Grains and Their Regulation by Polyamines and Phytohormones

“…The mechanism by which BRs positively regulate the biosynthesis of amino acids in rice is not very clear. There are reports showing that BRs could increase energy charge by enhancing adenosine triphosphatase (ATPase, EC 3.6.1.3) activity, and that BRs could maintain redox homeostasis by enhancing the activities of enzymes involved in the ascorbate-glutathione (AsA-GSH) cycle, including glutathione reductase (EC 1.6.4.2) and monodehydroascorbate reductase (EC 1.6.5.4), and the expression of genes encoding these enzymes [91][92][93]. It is proposed that BRs can antagonize with ethylene, thereby minimizing the inhibitory effect of ethylene on amino acid biosynthesis in plants [93].…”

Brassinosteroids mediate moderate soil‐drying to alleviate spikelet degeneration under high temperature during meiosis of rice

“…Redox imbalance can decrease the intracellular antioxidant capacity and induce ROS burst, and therefore, result in injury in the membrane system and protein structure, organelle degeneration and programmed cell death (PCD) (Zhang et al, 2011). The hydrogen peroxide (H 2 O 2 ) as the most stable and main ROS is believed to be the main factor causing spikelet degeneration in rice (Heng et al, 2018; Zhang et al, 2019a, 2019b, 2020a, 2020b). In higher plants, the ascorbate (ascorbic acid)–glutathione (AsA–GSH) cycle as the heart of the redox hub plays a crucial role in eliminating the overproduction of ROS (especially H 2 O 2 ) and ensures the balance of the intracellular environment, especially under abiotic stress (Foyer & Halliwell 1976; Foyer & Noctor 2011; Nicholas & Dominique 2019; Porcher et al, 2021; Suzuki et al, 2012).…”

“…The hydrogen peroxide (H 2 O 2 ) as the most stable and main ROS is believed to be the main factor causing spikelet degeneration in rice (Heng et al, 2018;Zhang et al, 2019aZhang et al, , 2019bZhang et al, , 2020aZhang et al, , 2020b. In higher plants, the ascorbate (ascorbic acid)-glutathione (AsA-GSH) cycle as the heart of the redox hub plays a crucial role in eliminating the overproduction of ROS (especially H 2 O 2 ) and ensures the balance of the intracellular environment, especially under abiotic stress (Foyer & Halliwell 1976;Foyer & Noctor 2011;Nicholas & Dominique 2019;Porcher et al, 2021;Suzuki et al, 2012).…”