Physiologia plantarum最新文献

Plant sphingolipids are lipophilic membrane components essential for different cellular functions but they also act as signaling molecules in various aspects of plant development. However, the interaction between plant sphingolipids and abscission remains largely uncharacterized. Here, the possible role of sphingolipids in regulating fruit abscission was examined in the abscission zone (AZ) of olive fruit. To this end, sphingolipid levels were manipulated through the application of exogenous sphingolipid long-chain bases (LCBs) or biosynthesis inhibitors, and their effects on fruit abscission as well as sphingolipid LCB/gene expression, hormones, reactive oxygen species (ROS) and cell death levels were examined in the AZ of olive fruit. Our data indicated that exogenous sphinganine (d18:0) induced fruit abscission, whereas the application of sphingosine (d18:1) or phytosphingosine (t18:0) or their phosphorylated derivatives did not have an effect on fruit abscission. Moreover, inhibition of LCB kinase or ceramide synthase, which increases sphingolipid LCB levels in the AZ, reduced fruit break strength. This induction of fruit abscission is associated with elevated ROS levels and cell death in the AZ enriched in salicylic acid (SA) and jasmonic acid (JA). Along the same line, programmed cell death (PCD) was particularly evident on the distal side of the AZ. These data suggest that endogenous d18:0 plays a key cellular role as signaling molecule functioning upstream of the SA/JA signaling pathway in mediating PCD spatially regulated in the AZ during fruit abscission. Overall, the findings reported here provide insight into the complex connection between PCD and plant sphingolipid LCBs, uncovering their interaction in the abscission process.

A common assumption of plant hydraulic physiology is that high hydraulic efficiency must come at the cost of hydraulic safety, generating a trade-off that raises doubts about the possibility of selecting both productive and drought-tolerant herbaceous crops. Wetland plants typically display high productivity, which requires high hydraulic efficiency to sustain transpiration rates coupled to CO₂ uptake. Previous studies have suggested high vulnerability to xylem embolism of different wetland plants, in line with expected trade-offs. However, some hygrophytes like Cyperus alternifolius L. can also experience prolonged periods of low water levels leading to substantial drought stress. We conducted an in-depth investigation of this species' hydraulic safety and efficiency by combining gas exchange measurements, hydraulic measurements of leaf hydraulic efficiency and safety, optical measurements of xylem vulnerability to embolism, and determination of cell turgor changes under drought. Our data confirm the high hydraulic efficiency of this wetland species, but at the same time, reveal its surprising drought tolerance in terms of turgor loss point and critical water potential values inducing xylem embolism and hydraulic failure, which were well below values inducing turgor loss and full stomatal closure. C. alternifolius emerges as a highly productive plant that is also well-equipped to tolerate drought via a combination of early stomatal closure and delayed onset of hydraulic damage. The species might represent a model plant to develop crops combining two of the most desirable traits in cultivated plants, i.e., high yield and significant drought tolerance.

Glycolate oxidase (GOX) is a crucial enzyme of photorespiration involving carbon metabolism and stress responses. It is poorly understood, however, how its activities are modulated in response to oxidative stress elicited by various environmental cues. Analysis of Arabidopsis catalase-defective mutant cat2 revealed that the GOX activities were gradually repressed during the growth, which were accompanied by decreased salicylic acid (SA)-dependent cell death, suggesting photorespiratory H₂O₂ may entrain negative feedback regulation of GOX in an age-dependent manner. Intriguingly, a loss-of-function mutation in GLYCOLATE OXIDASE1 (GOX1) rather than in GOX2 and GOX3 attenuated the SA responses of cat2. We found that GOX1 is S-nitrosylated at Cys-343 during consecutive oxidative stress in the cat2 mutant. Subsequently, increased GOX1-SNO formations may contribute to progressively decreased GOX activities and then compromised photorespiratory H₂O₂ flux, which forms a negative feedback loop limiting the amplified activation of SA-dependent defence responses. Together, the data reveal that GOX S-nitrosylation is involved in the crosstalk between photorespiratory H₂O₂ and NO signalling in the fine-tuning regulation of oxidative stress responses and further highlight that NO-based S-nitrosylation acts as an on-off switch for ROS homeostasis.

A partly infected plant becomes more resistant to subsequent infections by developing systemic acquired resistance (SAR). Primary infected tissues produce signals that travel to systemic tissues for SAR-associated priming of defense-related genes. The mechanism through which mobile signals contribute to long-lasting infection memory is mostly unknown. RSI1/FLD, a putative histone demethylase, is required for developing SAR. Here, we report that two other FLD homologs, LSD1-LIKE2 (LDL2) and POLYAMINE OXIDASE 5 (PAO5), are required for SAR development. The mutants of LDL2 and PAO5 are not defective in local resistance but are specifically impaired for SAR. The mutants are defective in salicylic acid accumulation and priming of defence-related genes such as PR1, FMO1, and SnRK2.8. LDL2 and PAO5 are expressed in systemic tissues upon SAR induction by pathogens or SAR mobile signal azelaic acid. The ldl2 and pao5 mutants generate SAR mobile signals like wild-type (WT) plants but fail to respond to the signal at the systemic leaves. Both LDL2 and PAO5 proteins contain polyamine oxidase (PAO) domains, suggesting their involvement in polyamine metabolism. Exogenous applications of polyamines such as spermine and spermidine activate SAR in WT and rescue SAR defects of ldl2 and pao5 plants. Inhibition of polyamine biosynthetic gene arginine decarboxylase blocks SAR development. Results altogether demonstrate specific non-redundant roles of LDL2 and PAO5 in SAR development with their possible involvement in polyamine metabolism.

Soybean isoflavones, natural phytoestrogens within the flavonoid family, exhibit diverse physiological benefits such as anticancer, antioxidant, and cardioprotective properties. Yet, the underlying biosynthetic pathways remain unclear. Research is required to get better knowledge of soybean isoflavone production and its potential uses. Our work thoroughly examined the R2R3-MYB subclass in soybean and discovered a new MYB transcription factor, GmMYB3a, which shares significant similarities with Arabidopsis MYB genes and regulates isoflavone biosynthesis. Our study reveals that GmMYB3a localizes to the nucleus and membrane, concurs with its potential involvement in the biosynthesis of isoflavones. Our analysis also indicated a synergistic expression pattern between GmMYB3a and seed development, thereby creating the hypothesis that it has a critical role in the regulation of isoflavone synthesis. Transgenic experiments further demonstrated that GmMYB3a positively regulates isoflavone biosynthesis and leads to its overexpression. GmMYB3a has been implicated in abiotic stress responses, affecting soybean stress tolerance. RNA sequencing analysis revealed that GmMYB3a regulates downstream genes involved in isoflavone, flavonoid, and phenylalanine metabolism, especially the key chalcone synthase genes, CHS7 and CHS8. Moreover, GmMYB3a was shown to be tightly associated with GmCHS7 and GmCHS8 expressions, potentially regulating them directly. Yeast two-hybrid screening identified GmMYB3a interacting proteins crucial for the synthesis of physiologically active substances and abiotic stress responses. Our results increase knowledge of the regulatory mechanisms of GmMYB3a and establish a molecular network involving GmMYB3a, GmCHS7, and GmCHS8, thereby offering novel strategies for improving soybean quality and stress-tolerant breeding.

During the last decades, the breeding of major crops is growing at a slower rate than desirable to meet future food demands in many agro-environments. Moreover, extreme climatic conditions, and particularly, drought impairments associated with climate change, are limiting the genetic gains of crops in temperate areas, especially in the Mediterranean basin. Drought events and atmospheric air temperatures and CO₂ concentrations are increasing at an accelerating pace. Unfortunately, not all breeding programmes have been oriented towards developing climate-resilient crops to cope with future climate predictions, so it is unclear how crops will respond under future multiple stress conditions. In this regard, special attention should be paid to the triple interaction effect of drought, elevated temperature and CO₂ concentration on plant responses. Our aim was i) to perform a systematic review of the existing literature on the physiological and agronomic responses of herbaceous plants, mainly grasses, legumes, and forbs to this triple interaction, and ii) elucidate general responses through a meta-analysis. The analysis of the literature unveils the great heterogeneity that exists in the experimental designs carried out to date to study multiple stress conditions in herbaceous plants, making it difficult to extrapolate general responses. A meta-analysis of a subset of studies that met the criteria of having grown plants under elevated CO₂ concentrations along the whole experiment suggests that the negative effects of drought on plant performance will be mitigated under future climate conditions, although the responses depend on the severity of the stressors and the experimental variables measured.

Salinity stress severely affects rice growth and reduces its productivity. With No Lysine Kinases (WNKs) are serine/threonine kinases emerging as potential candidate genes due to their involvement in various abiotic stress tolerance responses. However, studies providing mechanistic insights into the roles of WNKs in plants remain scarce. In the present study, OsWNK9-overexpressing rice lines showed strong tolerance to salinity stress. Overexpression of OsWNK9 also triggered the accumulation of abscisic acid (ABA) and restored indole-3-acetic acid (IAA) concentrations in roots, triggering stomatal closure in shoots and maintaining cell expansion of the root epidermal cells when challenged with salt treatment. The overexpression lines showed increased activity of antioxidant enzymes, which further mitigated ROS-mediated cellular damage under salinity stress. We also identified that OsWNK9 interacts with Receptor for Activated Kinase C1A (RACK1A), ABA-8'-hydroxylase, and (Vacuolar Type ATPase) V-Type ATPase. Taken together, our findings suggest that OsWNK9 expression is warranted under salinity stress and exerts its effects by interacting with its downstream targets and by increased accumulation of ABA and IAA, thereby regulating seed germination, stomatal activity, improved root growth, and ionic homeostasis, which all contribute to significantly higher yield produced per plant under long term salinity stress.

Water is the basic molecule in living beings, and it has a major impact on vital processes. Plants are sessile organisms with a sophisticated regulatory network that regulates how resources are distributed between developmental and adaptation processes. Drought-stressed plants can change their survival strategies to adapt to this unfavorable situation. Indeed, plants modify, change, and modulate gene expression when grown in a low-water environment. This adaptation occurs through several mechanisms that affect the expression of genes, allowing these plants to resist in dry regions. Epigenetic modulation has emerged as a major factor in the transcription regulation of drought stress-related genes. Moreover, specific molecular and epigenetic modifications in the expression of certain genetic networks lead to adapted responses that aid a plant's acclimatization and survival during repeated stress. Indeed, understanding plant responses to severe environmental stresses, including drought, is critical for biotechnological applications. Here, we first focused on drought stress in plants and their general adaptation mechanisms to this stress. We also discussed plant epigenetic regulation when exposed to water stress and how this adaptation can be passed down through generations.

Steryl esters (SE) are a storage pool of sterols that accumulates in cytoplasmic lipid droplets and helps to maintain plasma membrane sterol homeostasis throughout plant growth and development. Ester formation in plant SE is catalyzed by phospholipid:sterol acyltransferase (PSAT) and acyl-CoA:sterol acyltransferase (ASAT), which transfer long-chain fatty acid groups to free sterols from phospholipids and acyl-CoA, respectively. Comparative mass spectrometry-based metabolomic analysis between ripe fruits and seeds of a tomato (Solanum lycopersicum cv Micro-Tom) mutant lacking functional PSAT and ASAT enzymes (slasat1xslpsat1) shows that disruption of SE biosynthesis has a differential impact on the metabolome of these organs, including changes in the composition of free and glycosylated sterols. Significant perturbations were observed in the fruit lipidome in contrast to the mild effect detected in the lipidome of seeds. A contrasting response was also observed in phenylpropanoid metabolism, which is down-regulated in fruits and appears to be stimulated in seeds. Comparison of global metabolic changes using volcano plot analysis suggests that disruption of SE biosynthesis favours a general state of metabolic activation that is more evident in seeds than fruits. Interestingly, there is an induction of autophagy in both tissues, which may contribute along with other metabolic changes to the phenotypes of early seed germination and enhanced fruit tolerance to Botrytis cinerea displayed by the slasat1xslpsat1 mutant. The results of this study reveal unreported connections between SE metabolism and the metabolic status of plant cells and lay the basis for further studies aimed at elucidating the mechanisms underlying the observed effects.

Calcium ions (Ca²⁺) are important second messengers and are known to participate in cold signal transduction. In the current study, we characterized a Ca²⁺-binding protein gene, VamCP1, from the extremely cold-tolerant grape species Vitis amurensis. VamCP1 expression varied among organs but was highest in leaves following cold treatment, peaking 24 h after treatment onset. VamCP1 was found to localize to the plasma membrane and nucleus and the gene showed transcriptional autoactivation activity. Overexpression of VamCP1 in Arabidopsis thaliana and grapevine (V. vinifera) resulted in transgenic plants that were more tolerant to cold stress than the wild type. This correlated with reduced accumulation of reactive oxygen species (ROS), elevated activity of antioxidant enzymes and proline content, as well as lower levels of malondialdehyde and electrolyte leakage. Additionally, the expression of genes related to cold tolerance, including C-repeat binding factors (CBF) and cold-regulated (COR) genes, was higher in the transgenic lines. Taken together, our results indicate that overexpression of VamCP1 enhanced cold tolerance in plants by promoting the upregulation of genes related to cold tolerance and scavenging of excessive ROS. These findings provide a foundation for the molecular breeding of cold-tolerant grapevine.