Journal of plant physiology最新文献

Potassium (K) deficiency occurs commonly in crop plants. Optimal K nutrition is particularly important when plants are exposed to stress conditions (especially drought and heat) because a cellular demand for K increases. Low K in plant tissues is known to aggravate the effects of drought stress by impairing the osmoregulation process and the photosynthetic carbon metabolism. However, despite numerous publications about the role of K in enhancing tolerance to drought stress in crop plants, our understanding of the major mechanisms underlying the stress-mitigating effects of K is still limited. This paper summarizes and appraises the current knowledge on the major protective effects of K under drought stress, and then proposes a new K-related drought stress-mitigating mechanism, whereby optimal K nutrition may promote partitioning of carbohydrates in stem tissues and subsequent mobilization of these carbohydrates into developing grain under drought stress. The importance of stem reserves of carbohydrates is based on limited photosynthetic capacity during the grain-filling period under drought conditions due to premature leaf senescence as well as due to impaired assimilate transport from leaves to the developing grains. Plants with a high capacity to store large amounts of soluble carbohydrates in stems before anthesis and mobilize them into grain post-anthesis have a high potential to yield well in dry and hot environments. In practice, particular attention needs to be paid to the K nutritional status of plants grown with limited water supply, especially during grain filling. Because K is the mineral nutrient deposited mainly in stem, a special consideration should be given to stems of crop plants in research dealing with the effects of K on yield formation and stress mitigation.

The growing worldwide population is driving up demand for cotton fibers, but production is hampered by unpredictable temperature rises caused by shifting climatic conditions. Numerous research based on breeding and genomics have been conducted to increase the production of cotton in environments with high and low-temperature stress. High temperature (HT) is a major environmental stressor with global consequences, influencing several aspects of cotton plant growth and metabolism. Heat stress-induced physiological and biochemical changes are research topics, and molecular techniques are used to improve cotton plants' heat tolerance. To preserve internal balance, heat stress activates various stress-responsive processes, including repairing damaged proteins and membranes, through various molecular networks. Recent research has investigated the diverse reactions of cotton cultivars to temperature stress, indicating that cotton plant adaptation mechanisms include the accumulation of sugars, proline, phenolics, flavonoids, and heat shock proteins. To overcome the obstacles caused by heat stress, it is crucial to develop and choose heat-tolerant cotton cultivars. Food security and sustainable agriculture depend on the application of genetic, agronomic, and, biotechnological methods to lessen the impacts of heat stress on cotton crops. Cotton producers and the textile industry both benefit from increased heat tolerance. Future studies should examine the developmental responses of cotton at different growth stages, emphasize the significance of breeding heat-tolerant cultivars, and assess the biochemical, physiological, and molecular pathways involved in seed germination under high temperatures. In a nutshell, a concentrated effort is required to raise cotton's heat tolerance due to the rising global temperatures and the rise in the frequency of extreme weather occurrences. Furthermore, emerging advances in sequencing technologies have made major progress toward successfully se sequencing the complex cotton genome.

Agriculture is vital for global food security, and irrigation is essential for improving crop yields. However, irrigation can pose challenges such as mineral scarcity and salt accumulation in the soil, which negatively impact plant growth and crop productivity. While numerous studies have focused on enhancing plant tolerance to high salinity, research targeting various ecotypes of Arabidopsis thaliana has been relatively limited. In this study, we aimed to identify salt-tolerant ecotypes among the diverse wild types of Arabidopsis thaliana and elucidate their characteristics at the molecular level. As a result, we found that Catania-1 (Ct-1), one of the ecotypes of Arabidopsis, exhibits greater salt tolerance compared to Col-0. Specifically, Ct-1 exhibited less damage from reactive oxygen species (ROS) than Col-0, despite not accumulating antioxidants like anthocyanins. Additionally, Ct-1 accumulated more potassium ions (K⁺) in its shoots and roots than Col-0 under high salinity, which is crucial for water balance and preventing dehydration. In contrast, Ct-1 plants were observed to accumulate slightly lower levels of Na⁺ than Col-0 in both root and shoot tissues, regardless of salt treatment. These findings suggest that Ct-1 plants achieve high salinity resistance not by extruding more Na⁺ than Col-0, but rather by absorbing more K⁺ or releasing less K⁺. Ct-1 exhibited higher nitrate (NO₃^-) levels than Col-0 under high salinity conditions, which is associated with enhanced retention of K⁺ ions. Additionally, genes involved in NO₃^- transport and uptake, such as NRT1.5 and NPF2.3, showed higher transcript levels in Ct-1 compared to Col-0 when exposed to high salinity. However, Ct-1 did not demonstrate significantly greater resistance to osmotic stress compared to Col-0. These findings suggest that enhancing plant tolerance to salt stress could involve targeting the cellular processes responsible for regulating the transport of NO₃^- and K⁺. Overall, our study sheds light on the mechanisms of plant salinity tolerance, emphasizing the importance of K⁺ and NO₃^- transport in crop improvement and food security in regions facing salinity stress.

Plants often face high salinity as a significant environmental challenge with roots being the first responders to this stress. Maintaining K⁺/Na⁺ ratio within plant cells is crucial for survival, as the intracellular K⁺ level decreases and the intracellular Na⁺ level increases under saline conditions. However, knowledge about the molecular regulatory mechanisms of K⁺ loss in response to salt stress through outward-rectifying K⁺ channels in plants is largely unknown. In this study, we found that the Arabidopsis double mutant gorkskor, in which the GORK and SKOR genes are disrupted, showed an improved primary root growth under salt stress compared to wild-type (WT) and the gork and skor single-mutant plants. No significant differences in the sensitivity to mannitol stress between the WT and gorkskor mutant were observed. Accumulation of ROS induced by salt stress was reduced in the gorkskor roots. The gorkskor mutant seedlings had significantly higher K⁺ content, lower Na⁺ content, and a greater resultant K⁺/Na⁺ ratio than the WT under salt stress. Moreover, salt-stress-induced elevation of cytosolic free Ca²⁺ concentration was reduced in the gorkskor roots. Taken together, these results suggest that Arabidopsis Shaker-type outward-rectifying K⁺ channels GORK and SKOR may redundantly function in regulation of primary root growth under salt stress and are involved in not only the late-stage response (e.g. K⁺ leakage) but also the early response including ROS production and [Ca²⁺]_cyt elevation.

Pathogen-responsive immune-related genes (resistance genes [R-genes]) and hormones are crucial mediators of systemic acquired resistance (SAR). However, their integrated functions in regulating SAR signaling components in local and distal leaves remain largely unknown. To characterize SAR in the Xanthomonas campestris pv. campestris (Xcc)–Brassica napus pathosystem, the responses of R-genes, (leaf and phloem) hormone levels, H₂O₂ levels, and Ca²⁺ signaling-related genes were assessed in local and distal leaves of plants exposed to four Xcc-treatments: Non-inoculation (control), only secondary Xcc-inoculation in distal leaves (C-Xcc), only primary Xcc-inoculation in local leaves (Xcc), and both primary and secondary Xcc-inoculation (X-Xcc). The primary Xcc-inoculation provoked disease symptoms as evidenced by enlarged destructive necrosis in the local leaves of Xcc and X-Xcc plants 7 days post-inoculation. Comparing visual symptoms in distal leaves 5 days post-secondary inoculation, yellowish necrotic lesions were clearly observed in non Xcc-primed plants (C-Xcc), whereas no visual symptom was developed in Xcc-primed plants (X-Xcc), demonstrating SAR. Pathogen resistance in X-Xcc plants was characterized by distinct upregulations in expression of the PAMP-triggered immunity (PTI)-related kinase-encoding gene, BIK1, the (CC-NB-LRR-type) R-gene, ZAR1, and its signaling-related gene, NDR1, with a concurrent enhancement of the kinase-encoding gene, MAPK6, and a depression of the (TIR-NB-LRR-type) R-gene, TAO1, and its signaling-related gene, SGT1, in distal leaves. Further, in X-Xcc plants, higher salicylic acid (SA) and jasmonic acid (JA) levels, both in phloem and distal leaves, were accompanied by enhanced expressions of the SA-signaling gene, NPR3, the JA-signaling genes, LOX2 and PDF1.2, and the Ca²⁺-signaling genes, CAS and CBP60g. However, in distal leaves of C-Xcc plants, an increase in SA level resulted in an antagonistic depression of JA, which enhanced only SA-dependent signaling, EDS1 and NPR1. These results demonstrate that primary Xcc-inoculation in local leaves induces resistance to subsequent pathogen attack by upregulating BIK1-ZAR1-mediated synergistic interactions with SA and JA signaling as a crucial component of SAR.

ABA-insensitive 5 (ABI5) belongs to the basic leucine zipper class of transcription factors and is named for being the fifth identified Arabidopsis mutant unresponsive to ABA. To understand the influence of ABI5 in its active state on downstream gene expression and plant growth and development, we overexpressed the full-length ABI5 (A.t.MX-4) and the active forms of ABI5 with deleted transcriptional repression domains (A.t.MX-1, A.t.MX-2, and A.t.MX-3). Compared with the wild type, A.t.MX-1, A.t.MX-2, and A.t.MX-3 exhibited an increase in rosette leaf number and size, earlier flowering, increased thousand-seed weight, and significantly enhanced drought resistance. Thirty-five upregulated/downregulated proteins in the A.t.MX-1 were identified by proteomic analysis, and these proteins were involved in ABA biosynthesis and degradation, abiotic stress, fatty acid synthesis, and energy metabolism. These proteins participate in the regulation of plant drought resistance, flowering timing, and seed size at the levels of transcription and post-translational modification.

Alfalfa often suffers from low temperature during spring rejuvenation, so it is important to improve the cold tolerance of alfalfa leaves for its smooth rejuvenation, and the alternative pathway (AP) could effectively improve the plant's tolerance. In this study, the contribution of AP on spring rejuvenation of alfalfa was investigated in Xinmu No.4 and Gannong No.5 with different fall dormancy levels. Though the protein and AP capacity were decreased during the rejuvenation, the ratio of AP/TP were increased in two alfalfa varieties, compared to those in alfalfa before overwintering. This indicated that AP had positive response to alfalfa rejuvenation. The limitation of AP significantly affected the leaf length, leaf width and growth rate of greening alfalfa, showing that AP played an important role in alfalfa rejuvenation. Inhibition of AP resulted in a significant decrease in Pn, Ci, Gs and stomatal structure deformity, suggestion that AP affected photosynthesis by influencing stomatal development during rejuvenation. AP reduces oxidative damage to PSII core protein repair in alfalfa leaves and optimizes photosynthesis by up-regulating NADP-MDH activity, decreasing the accumulation of excess reducing power in the chloroplasts, and by increasing SOD and POD activities and decreasing the accumulation of hydrogen peroxide. The higher proportion of AP keeps it more tolerant to low temperature for rejuvenation in Xinmu No.4 with a lower fall dormancy level.

Flavonoid compounds are widely present in various organs and tissues of different plants, playing important roles when plants are exposed to abiotic stresses. Different types of flavonoids are biosynthesized by a series of enzymes that are encoded by a range of gene families. In this study, a total of 63 flavonoid pathway genes were identified from the genome of Medicago truncatula. Gene structure analysis revealed that they all have different gene structure, with most CHS genes containing only one intron. Additionally, analysis of promoter sequences revealed that many cis-acting elements responsive to abiotic stress are located in the promoter region of flavonoid pathway genes. Furthermore, analysis on M. truncatula gene chip data revealed significant changes in expression level of most flavonoid pathway genes under the induction of salt or drought treatment. qRT-PCR further confirmed significant increase in expression level of several flavonoid pathway genes under NaCl and mannitol treatments, with CHS1, CHS9, CHS10, F3′H4 and F3′H5 genes showing significant up-regulation, indicating they are key genes in response to abiotic stress in M. truncatula. In summary, our study identified key flavonoid pathway genes that were involved in salt and drought response, which provides important insights into possible modification of flavonoid pathway genes for molecular breeding of forage grass with improved abiotic resistance.

NHX5 and NHX6, Arabidopsis endosomal antiporters, play a vital role in facilitating ion and pH homeostasis in endosomal compartments. Studies have found that NHX5 and NHX6 are essential for protein trafficking, auxin homeostasis, and plant growth and development. Here, we report the role of NHX5 and NHX6 in brassinosteroid (BR) signaling. We found that hypocotyl growth was enhanced in nhx5 nhx6 under epibrassinolide (eBR) treatment. nhx5 nhx6 bri1 was insensitive to eBR treatment, indicating that NHX5 and NHX6 are downstream of the BRI1 receptor in BR signaling. Moreover, confocal observation with both hypocotyls and root tips showed that BRI1-YFP localization in the plasma membrane (PM) was reduced in nhx5 nhx6. Interestingly, brefeldin A (BFA) treatment showed that formation of the BFA bodies containing BRI1 and their disassembling were disrupted in nhx5 nhx6. Further genetic analysis showed that NHX5/NHX6 and SYP22 may act coordinately in BR signaling. NHX5 and NHX6 may regulate SYP22 function by modulating cellular K⁺ and pH homeostasis. Importantly, NHX5 and NHX6 colocalize and interact with SYP22, but do not interact with BRI1. In summary, our findings indicate that NHX5/NHX6/SYP22 complex is essential for the regulation of BRI1 recycling and PM localization. The H⁺-leak facilitated by NHX5 and NHX6 offers a means of controlling BR signaling in plants.

Common vetch (Vicia sativa L.) is widely planted as forage, green manure and food. Phosphate (Pi) deficiency is an important constraint for legume crop production. In this study, P-deficiency tolerance in 40 common vetch collections was evaluated under hydroponic condition. The collections were clustered into three groups based on the tolerance level. Physiological responses to P-deficiency in two tolerant collections (418 and 426) in comparison with one sensitive collection (415) were investigated. Greater growth inhibition was observed in sensitive collection compared with two tolerant collections, although the inorganic phosphorus (P) content in sensitive collection was higher than those in tolerant collections. The internal and external purple acid phosphatase activity in plants showed no significant difference between 418 and 415 under low phosphate condition. Transcriptomic analysis in the tolerant collection 426 in response to Pi starvation showed that many common adaptive strategies were applied and PHOSPHATE STARVATION RESPONSE (PHR)-related Pi signaling and transporter genes were altered. VsPHT1.2 had the highest expression level in root among all VsPHT1s, and it was remarkably upregulated after short time of P-deficiency treatment in tolerant collections compared with sensitive collection. In conclusion, common vetch response to P starvation by altering the expressions of core genes involved in Pi transport and signaling, and the elevated expression of VsPHT1.2 gene might contribute to higher Pi acquisition efficiency in P-deficiency tolerant collections.