High temperatures (HT) cause pollen abortion and poor floret fertility in rice, which is closely associated with excessive accumulation of reactive oxygen species (ROS) in the developing anthers. ...However, the relationships between accumulation of abscisic acid (ABA) and ROS, and their effects on tapetum‐specific programmed cell death (PCD) in HT‐stressed anthers are poorly characterised. Here, we determined the spatiotemporal changes in ABA and ROS levels, and their relationships with tapetal PCD under HT exposure. Mutants lacking ABA‐activated protein kinase 2 (SAPK2) functions and exogenous ABA treatments were used to explore the effects of ABA signalling on the induction of PCD and ROS accumulation during pollen development. HT‐induced pollen abortion was tightly associated with ABA accumulation and oxidative stress. The higher ABA level in HT‐stressed anthers resulted in the earlier initiation of PCD induction and subsequently abnormal tapetum degeneration by activating ROS accumulation in developing anthers. Interactions between SAPK2 and DEAD‐box ATP‐dependent RNA helicase elF4A‐1 (RH4) were required for ABA‐induced ROS generation in developing anthers. The OsSAPK2 knockout mutants showed the impaired PCD responses in the absence of HT. However, the deficiency of SAPK2 functions did not suppress the ABA‐mediated ROS generation in HT‐stressed anthers.
Summary statement
High temperatures (HT) disturbed the cellular distributions of ABA and ROS contents in rice anthers. The higher ABA in HT‐stressed anthers contributed to HT‐induced pollen abortion by activating ROS generation and oxidation in developing anthers. Interactions between SAPK2 and DEAD‐box ATP‐dependent RNA helicase elF4A‐1 (RH4) were required for ABA‐induced ROS generation during pollen development and its response to HT exposure.
The breeding of low phytic acid (LPA) crops is widely considered an effective strategy to improve crop nutrition, but the LPA crops usually have inferior seed germination performance. To clarify the ...reason for the suboptimal seed performance of LPA rice, this study investigated the impact of reduced seed phytic acid (InsP6) content in rice ins(3)P synthase1 (EC 5.5.1.4, RINO1), one of the key targets for engineering LPA rice, knockouton cellular differentiation in seed embryos and its relation to myo‐inositol metabolism and auxin signalling during embryogenesis. The results indicated that the homozygotes of RINO1 knockout could initiate differentiation at the early stage of embryogenesis but failed to form normal differentiation of plumule and radicle primordia. The loss of RINO1 function disrupted vesicle trafficking and auxin signalling due to the significantly lowered phosphatidylinositides (PIs) concentration in seed embryos, thereby leading to the defects of seed embryos without the recognizable differentiation of shoot apex meristem (SAM) and radicle apex meristem (RAM) for the homozygotes of RINO1 knockout. The abnormal embryo phenotype of RINO1 homozygotes was partially rescued by exogenous spraying of inositol and indole‐3‐acetic acid (IAA) in rice panicle. Thus, RINO1 is crucial for both seed InsP6 biosynthesis and embryonic development. The lower phosphatidylinositol (4,5)‐bisphosphate (PI (4,5) P2) concentration and the disorder auxin distribution induced by insufficient inositol supply in seed embryos were among the regulatory switch steps leading to aberrant embryogenesis and failure of seed germination in RINO1 knockout.
Nitrogen (N) deficiency is one of the critical environmental factors that induce leaf senescence, and its occurrence may cause the shorten leaf photosynthetic period and markedly lowered grain yield. ...However, the physiological metabolism underlying N deficiency-induced leaf senescence and its relationship with the abscisic acid (ABA) concentration and reactive oxygen species (ROS) burst in leaf tissues are not well understood. In this paper, the effect of N supply on several senescence-related physiological parameters and its relation to the temporal patterns of ABA concentration and ROS accumulation during leaf senescence were investigated using the premature senescence of flag leaf mutant rice (
psf
) and its wild type under three N treatments. The results showed that N deficiency hastened the initiation and progression of leaf senescence, and this occurrence was closely associated with the upregulated expression of 9-cis-epoxycarotenoiddioxygenase genes
(NCEDs)
and with the downregulated expression of two ABA 8′-hydroxylase isoform genes (
ABA8ox2
and
ABA8ox3)
under LN treatment. Contrarily, HN supply delayed the initiation and progression of leaf senescence, concurrently with the suppressed ABA biosynthesis and relatively lower level of ABA concentration in leaf tissues. Exogenous ABA incubation enhanced ROS generation and MDA accumulation in a dose-dependent manner, but it decreased the activities of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) in detached leaf. These results suggested that the participation of ABA in the regulation of ROS generation and N assimilating/remobilizing metabolism in rice leaves was strongly responsible for induction of leaf senescence by N deficiency.
Flavonoids are phytochemical compounds present in many plants, fruits, vegetables, and leaves, with potential applications in medicinal chemistry. Flavonoids possess a number of medicinal benefits, ...including anticancer, antioxidant, anti-inflammatory, and antiviral properties. They also have neuroprotective and cardio-protective effects. These biological activities depend upon the type of flavonoid, its (possible) mode of action, and its bioavailability. These cost-effective medicinal components have significant biological activities, and their effectiveness has been proved for a variety of diseases. The most recent work is focused on their isolation, synthesis of their analogs, and their effects on human health using a variety of techniques and animal models. Thousands of flavonoids have been successfully isolated, and this number increases steadily. We have therefore made an effort to summarize the isolated flavonoids with useful activities in order to gain a better understanding of their effects on human health.
Low phytic acid (lpa) crop is considered as an effective strategy to improve crop nutritional quality, but a substantial decrease in phytic acid (PA) usually has negative effect on agronomic ...performance and its response to environment adversities. Myo-inositol-3-phosphate synthase (MIPS) is the rate-limiting enzyme in PA biosynthesis pathway, and regarded as the prime target for engineering lpa crop. In this paper, the rice MIPS gene (RINO2) knockout mutants and its wild type were performed to investigate the genotype-dependent alteration in the heat injury-induced spikelet fertility and its underlying mechanism for rice plants being imposed to heat stress at anthesis. Results indicated that RINO2 knockout significantly enhanced the susceptibility of rice spikelet fertility to heat injury, due to the severely exacerbated obstacles in pollen germination and pollen tube growth in pistil for RINO2 knockout under high temperature (HT) at anthesis. The loss of RINO2 function caused a marked reduction in inositol and phosphatidylinositol derivative concentrations in the HT-stressed pollen grains, which resulted in the strikingly lower content of phosphatidylinositol 4,5-diphosphate (PI (4,5) P
) in germinating pollen grain and pollen tube. The insufficient supply of PI (4,5) P
in the HT-stressed pollen grains disrupted normal Ca
gradient in the apical region of pollen tubes and actin filament cytoskeleton in growing pollen tubes. The severely repressed biosynthesis of PI (4,5) P
was among the regulatory switch steps leading to the impaired pollen germination and deformed pollen tube growth for the HT-stressed pollens of RINO2 knockout mutants.
High temperature (HT) at meiosis stage is one of most important environment constraint affecting spikelet fertility and rice yield. In this paper, the effects of HT exposure at meiosis stage on the ...ROS (reactive oxygen species) accumulation, various superoxide dismutase (SOD, EC1.15.1.11) isozymes in developing anther, and its relationship with HT-induced decline in pollen viability and floret fertility were investigated by using four rice cultivars differing in heat tolerance under well-controlled climatic condition. Results showed that HT exposure significantly increased ROS level and malondialdehyde (MDA) content in rice anther, and this occurrence was strongly responsible for the HT-induced decline in pollen viability and harmful effect of HT adversity on floret fertility. However, the increased extent of ROS concentration in rice anther under HT exposure was greatly variable, depending on both the intensity and duration of HT exposure and different rice cultivars used. The SOD and CAT activities of HT-sensitive cultivars decreased more profoundly than those of HT-tolerant cultivars under the same HT regimes. Among various types of SOD enzymes, Cu/Zn–SODa expressed highly in rice anther and responded sensitively to HT exposure, while Cu/Zn–SODb expressed weakly in rice anther and preferentially in rice leaves. HT exposure suppressed the expression of Cu/Zn–SODa in developing anther, which was closely associated with the down-regulated transcripts of cCu/Zn–SOD1 gene. Hence, Cu/Zn–SODa may play a central role in the regulation of total SOD activity and ROS detoxification in rice anther as affected by HT exposure at meiosis stage.
•ROS in rice anther was closely related to cultivar specific change in HT injury.•Cu/Zn-SODa dominated SOD activity in anther and responded sensitively to HT stress.•HT stress regulated Cu/Zn-SODa in anther at both protein and transcript level.•Cu/Zn-SODb contributed slightly to HT-induced ROS scavenging in rice anther.
The translocation of nonstructural carbohydrates (NSC) from leaf sheaths to filling grains after anthesis contributed greatly to the grain yield of cereal crops. In this study, the effect of nitrogen ...(N) supply levels on the accumulation and translocation of NSC in leaf sheath tissues and its relationship with the initiation and progression of leaf senescence during grain filling was investigated using two rice (Oryza sativa L.) genotypes, namely, premature flag leaf senescence mutant (psf) and its wild‐type. Three N treatment levels were used to examine N‐supply induced alteration in the activities of several key enzymes involved in NSC translocation and N assimilation in different leaf sheaths. The results show that the NSC translocation rate in leaf sheaths under low nitrogen (LN) treatment was significantly higher than those under normal nitrogen (NN) and high nitrogen (HN) treatments. However, the positive effect of LN on the NSC translocation in leaf sheath was closely associated with its negative effect on grain yield, due to accelerated leaf senescence and shortened leaf longevity. Comparatively, the upper‐positional sheath had a lower NSC amount and higher NSC translocation rate than the lower‐leaf sheaths after heading. High N suppressed sucrose‐phosphate synthase (SPS) activity in leaf sheaths, but enhanced the activity of key enzymes involving in N assimilation in leaf sheaths. The upper sheath had higher activity of sucrose‐metabolizing enzymes and lower activity of N‐assimilating enzymes. Hence, the upper‐leaf sheath had a relatively weak N assimilation and stronger NSC translocation than the lower‐leaf sheaths.
Abiotic stresses trigger premature leaf senescence by affecting some endogenous factors, which is an important limitation for plant growth and grain yield. Among these endogenous factors that ...regulate leaf senescence, abscisic acid (ABA) works as a link between the oxidase damage of cellular structure and signal molecules responding to abiotic stress during leaf senescence. Considering the importance of ABA, we collect the latest findings related to ABA biosynthesis, ABA signaling, and its inhibitory effect on chloroplast structure destruction, chlorophyll (Chl) degradation, and photosynthesis reduction. Post-translational changes in leaf senescence end with the exhaustion of nutrients, yellowing of leaves, and death of senescent tissues. In this article, we review the literature on the ABA-inducing leaf senescence mechanism in rice and
starting from ABA synthesis, transport, signaling receptors, and catabolism. We also predict the future outcomes of investigations related to other plants. Before changes in translation occur, ABA signaling that mediates the expression of
,
, and
transcription factors (TFs) has been investigated to explain the inducing effect on senescence-associated genes. Various factors related to calcium signaling, reactive oxygen species (ROS) production, and protein degradation are elaborated, and research gaps and potential prospects are presented. Examples of gene mutation conferring the delay or induction of leaf senescence are also described, and they may be helpful in understanding the inhibitory effect of abiotic stresses and effective measures to tolerate, minimize, or resist their inducing effect on leaf senescence.
During the last two decades the world has experienced an abrupt change in climate. Both natural and artificial factors are climate change drivers, although the effect of natural factors are lesser ...than the anthropogenic drivers. These factors have changed the pattern of precipitation resulting in a rise in sea levels, changes in evapotranspiration, occurrence of flood overwintering of pathogens, increased resistance of pests and parasites, and reduced productivity of plants. Although excess CO
2
promotes growth of C
3
plants, high temperatures reduce the yield of important agricultural crops due to high evapotranspiration. These two factors have an impact on soil salinization and agriculture production, leading to the issue of water and food security. Farmers have adopted different strategies to cope with agriculture production in saline and saline sodic soil. Recently the inoculation of halotolerant plant growth promoting rhizobacteria (PGPR) in saline fields is an environmentally friendly and sustainable approach to overcome salinity and promote crop growth and yield in saline and saline sodic soil. These halotolerant bacteria synthesize certain metabolites which help crops in adopting a saline condition and promote their growth without any negative effects. There is a complex interkingdom signaling between host and microbes for mutual interaction, which is also influenced by environmental factors. For mutual survival, nature induces a strong positive relationship between host and microbes in the rhizosphere. Commercialization of such PGPR in the form of biofertilizers, biostimulants, and biopower are needed to build climate resilience in agriculture. The production of phytohormones, particularly auxins, have been demonstrated by PGPR, even the pathogenic bacteria and fungi which also modulate the endogenous level of auxins in plants, subsequently enhancing plant resistance to various stresses. The present review focuses on plant-microbe communication and elaborates on their role in plant tolerance under changing climatic conditions.
High temperature (HT) at meiosis induces heat injury to pollen viability and floret fertility, which is closely associated with HT-induced endoplasmic reticulum (ER) stress and ROS damage in ...developing anthers. Disulfide isomerase like proteins (PDILs) play an essential role in the formation, reduction, and isomerization of disulfide bonds in nascent secretory proteins for the maintenance of cell viability and ER homeostasis. However, the underlying mechanism by which HT induces ROS burst in rice anthers and its relation to ER stress for the varying existence of PDILs is largely unknown. In this paper, we investigated the action of PDILs in the regulation of heat injury to floret fertility and its association with HT-induced ROS generation in developing anthers under well-controlled climatic conditions. Results showed that knock-down of OsPDIL1–1 by RNAi enhanced the activity of NADPH oxidase and caused the excessive ROS accumulation in developing anthers, consequently the up-grading sensitivity of pollen viability and floret fertility to heat stress. RBOHb is the primary site where HT exposure affected NADPH oxidase activity and triggered ROS generation in rice anthers because OsPDIL1–1 was found to interact with RBOHb in the ER-PM junction. Furthermore, HT exposure triggered the RBOHb-mediated ROS generation in a Ca2+-dependent manner, while the induction of HT exposure to ER stress was not necessarily associated with ROS generation derived from NADPH oxidase.
•PDIL1-1 was essential for maintaining floret fertility at elevated temperatures.•PDIL1-1 directly interacts with RBOHb to modulate ROS generation in rice anthers.•HT triggered the RBOHb-mediated ROS generation in a Ca2+-dependent manner.•HT-induced ER stress was not associated with NADPH oxidase-derived ROS.•PDIL1-1 was found to interact with RBOHb in the ER-PM junction.
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