Journal of plant physiology最新文献

Fruit ripening in tomato is a highly coordinated developmental process accompanied with fruit softening, which is closely associated with cell wall degradation and remodeling. Xyloglucan endotransglucosylase/hydrolases (XTHs) are known to play an essential role in cell wall xyloglucan metabolism. Tomato XTH5 exhibits xyloglucan endotransglucosylase (XET) activity in vitro, but the understanding of its biological role in fruit ripening remains unclear. In this study, we revealed that SlXTH5 is highly expressed in mature fruits. Knockout mutant plants of SlXTH5 were generated by CRISPR/Cas9 gene editing strategy in tomato cultivar Micro-Tom. The mutant fruits showed accelerated transition from unripe to ripe process and earlier ethylene accumulation compared to wild type fruits. Although the mutation of SlXTH5 did not affect the size, weight and number of fruits, it indeed increased fruit firmness and extended shelf life, which is probably attributed to the increased cell layer and cell wall thickness of pericarp tissue. Pathogen infection experiment showed the enhanced resistance of mutant fruits to Botrytis cinerea. These results revealed the role of SlXTH5 in fruit ripening process, and provide new insight into how cell wall metabolism and remodeling regulate fruit softening and shelf life.

Reducing nitrogen (N) application is crucial in addressing the low N utilization efficiency (NUE) and the risks of environmental pollution in wheat production. Improving low N (LN) tolerance in wheat can help balance the conflict between wheat growth and reduced N fertilization. Hydroponic experiments were conducted using Yangmai158 (LN-tolerant) and Zaoyangmai (LN-sensitive) cultivars to study whether LN priming (LNP) in the 3-leaf stage can improve the photosynthetic capacity of wheat seedlings under N-deficit stress at the 5-leaf stage. LNP increased the net photosynthetic rate (P_n), stomatal conductance (G_s), electron transfer rate (ETR), carboxylation efficiency (CE), maximum carboxylation rate (V_cmax), and the content and activity of Rubisco and Rubisco activase (RCA) in both cultivars, with Yangmai158 showing a greater increase than Zaoyangmai. After 14 days of N-deficit stress, the decreases in P_n, G_s, ETR, CE, V_cmax, and the content and activity of Rubisco and RCA of the two cultivars treated with LNP were significantly lower compared with those of the treatments without LNP. LNP improved the allocation proportion of leaf N to photosynthetic machinery, with the greatest increase in the carboxylation machinery. These results indicate that LNP can allocate more N to the photosynthetic apparatus, improving Rubisco content and activity to enhance the photosynthetic capacity and NUE of leaves under N-deficit stress.

Ethylene (ET) and gibberellins (GAs) play key roles in controlling the biotic and abiotic interactions between plants and environment. To gain insights about the role of ET and GAs interactions in the mycorrization and response to salinity of tomato (Solanum lycopersicum L.) plants, the ET-insensitive (Never-ripe, Nr), and the ET-overproducer (Epinastic, Epi) mutants and their wild type cv. Micro-Tom (MT), were inoculated or not with the arbuscular mycorrhizal fungi (AMF) Rhizophagus irregularis and exposed to control (0 mM NaCl) and salinity (100 mM NaCl) conditions, with and without gibberellic acid (10⁻⁶ M GA₃) application during four weeks. Exogenous GA₃ enhanced plant growth irrespective of the genotype, AMF, and salinity conditions, while an additional effect on growth by AMF was only found in the ET-overproducer (Epi) mutant under control and salinity conditions. Epi almost doubled the AMF colonization level under both conditions but was the most affected by salinity and GA₃ application compared to MT and Nr. In contrast, Nr registered the lowest AMF colonization level, but GA₃ produced a positive effect, particularly under salinity, with the highest leaf growth recovery. Foliar GA₃ application increased the endogenous concentration of GA₁, GA₃, and total GAs, more intensively in AMF-Epi plants, where induced levels of the ET-precursor ACC were also found. Interestingly, GA₄ which is associated with AMF colonization, registered the strongest genotype x GA x AMF × salinity interactions. The different growth responses in relation to those interactions are discussed.

Drought stress limits plant growth and development. To cope with drought stress, abscisic acid (ABA) accumulates in plants. Although ABA-dependent drought tolerance pathways have been widely investigated, the feedback mechanisms and the negative regulatory roles within these pathways remain largely unknown. Here we characterize the roles of a C2H2 transcription factor, ZFP8, whose expression is repressed by ABA in the tolerance of drought stress. ZFP8-overexpressing plants were hyposensitive to ABA and exhibited less dehydration tolerance while ABA or drought-induced marker genes were more highly expressed in zfp8, suggesting that ZFP8 functions as a negative regulator in the ABA-mediated drought response. A transcriptome assay showed that ZFP8 positively regulates gene expression for cellular function and negatively regulates hormone and stress response gene expression. Moreover, we found that ZFP8 can interact with ABF2, one of the basic leucine zipper (bZIP) family transcription factor members, to inhibit its transcription activity. In conclusion, our results demonstrate a novel negative regulation pathway of ZFP8, which contributes to plants’ ability to fine-tune their drought responses.

Phosphorus deficiency usually promotes root:shoot ratio and sugar accumulation. However, how the allocation and utilization of carbon assimilates are regulated by phosphorus deficiency remains unclear. To understand how phosphorus deficiency affects the allocation and utilization of carbon assimilates, we systematically investigated the fixation and utilization of carbon, along with its diurnal and spatial patterns, in hydroponically grown maize seedlings under low phosphorus treatment. Under low phosphorus, sucrolytic activity was slightly inhibited by 12.0% in the root but dramatically inhibited by 38.8% in the shoot, corresponding to the promoted hexose/sucrose ratio and biomass in the root. Results point to a stable utilization of sucrose in the root facilitating competition for more assimilates, while increasing root:shoot ratio. Moreover, starch and sucrose accumulated in the leaves under low phosphorus. Spatially, starch and sucrose were oppositely distributed, starch mainly in the leaf tip, and sucrose mainly in the leaf base and sheath. Evidence of sucrose getting stuck in leaf base and sheath suggests that carbon accumulation is not attributed to carbon assimilation or export disturbance, but may be due to poor carbon utilization in the sinks. These findings improve the understanding of how low phosphorus regulates carbon allocation between shoot and root for acclimation to stress, and highlight the importance of improving carbon utilization in sinks to deal with phosphorus deficiency.

Although copper (Cu) is an essential microelement for plant growth and development, excess Cu results in a dramatic reduction in crop yield and quality. In the present study, we report that rice germin-like protein 8-7 (OsGLP8-7) plays a crucial role against Cu toxicity. The results showed that the transcriptional expression of the OsGLP8-7 gene was remarkably upregulated in the root and leaf by Cu treatment. The depletion of OsGLP8-7 significantly decreased the elongation of the primary root and plant height of rice under excess Cu. This hypersensitivity of osglp8-7 mutants towards excess Cu may be attributed to the weaker Cu retention in the cell wall compared with wild-type rice (Dongjin, DJ). Consistently, Cu-induced phenylpropanoid biosynthesis was compromised in osglp8-7 mutants based on RNA-Seq and qRT-PCR analysis. Furthermore, osglp8-7 mutants displayed a reduction of lignin deposition in the cell wall, and subsequently altered cell morphology. Osglp8-7 mutant lines also had higher Cu-induced O₂^•− and H₂O₂ levels than those of DJ under Cu stress. The results suggest that OsGLP8-7 participates in lignin synthesis for the acclimation to excess Cu. These findings provide a better understanding of a novel mechanism of germin-like proteins in the alleviation of heavy metal toxicity in rice.

In vitro plant embryogenesis and microcallus formation are systems which are required for plant regeneration, a process during which cell reprogramming and proliferation are critical. These systems offer many advantages in breeding programmes, such as doubled-haploid production, clonal propagation of selected genotypes, and recovery of successfully gene-edited or transformed plants. However, the low proportion of reprogrammed cells in many plant species makes these processes highly inefficient. Here we report a new strategy to improve in vitro plant cell reprogramming using small molecule inhibitors of mammalian leucine rich repeat kinase 2 (LRRK2), which are used in pharmaceutical applications for cell reprogramming, but never used in plants before. LRRK2 inhibitors increased in vitro embryo production in three different systems and species, microspore embryogenesis of oilseed rape and barley, and somatic embryogenesis in cork oak. These inhibitors also promoted plant cell reprogramming and proliferation in Arabidopsis protoplast cultures. The benzothiazole derivative JZ1.24, a representative compound of the tested molecules, modified the expression of the brassinosteroid (BR)-related genes BIN2, CPD, and BAS1, correlating with an activation of BR signaling. Additionally, the LRRK2 inhibitor JZ1.24 induced the expression of the embryogenesis marker gene SERK1-like. The results suggest that the use of small molecules from the pharmaceutical field could be extended to promote in vitro reprogramming of plant cells towards embryogenesis or microcallus formation in a wider range of plant species and in vitro systems. This technological innovation would help to develop new strategies to improve the efficiency of in vitro plant regeneration, a major bottleneck in plant breeding.

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.