Effect of shading on physiological attributes and comparative transcriptome analysis of Camellia sinensis cultivar reveals tolerance mechanisms to low temperatures

Molecular traits of MAPK kinases and the regulatory mechanism of GhMAPKK5 alleviating drought/salt stress in cotton

Mitogen-activated protein kinase kinases (MAPKKs) play a critical role in the mitogen-activated protein kinase (MAPK) signaling pathway, transducing external stimuli into intracellular responses and enabling plant adaptation to environmental challenges. Most research has focused on the model plant Arabidopsis (Arabidopsis thaliana). The systematic analysis and characterization of MAPKK genes across different plant species, particularly in cotton (Gossypium hirsutum), are somewhat limited. Here, we identified MAPKK family members from 66 different species, which clustered into five different sub-groups, and MAPKKs from four cotton species clustered together. Through further bioinformatic and expression analyses, GhMAPKK5 was identified as the most responsive MAPKK member to salt and drought stress among the 23 MAPKKs identified in Gossypium hirsutum. Silencing GhMAPKK5 in cotton through virus-induced gene silencing (VIGS) led to quicker wilting under salt and drought conditions, while overexpressing GhMAPKK5 in Arabidopsis enhanced root growth and seed germination under these stresses, demonstrating GhMAPKK5's positive role in stress tolerance. Transcriptomics and Yeast-Two-Hybrid assays revealed a MAPK cascade signal module comprising GhMEKK (mitogen-activated protein kinase kinase kinases)3/8/31-GhMAPKK5-GhMAPK11/23. This signaling cascade may play a role in managing drought and salt stress by regulating transcription factor genes, such as WRKYs, which are involved in the biosynthesis and transport pathways of ABA, proline, and RALF. This study is highly important for further understanding the regulatory mechanism of MAPKK in cotton, contributing to its stress tolerance and offering potential in targets for genetic enhancement.

Plant membrane transporters function under abiotic stresses: a review

MAIN CONCLUSION

In the present review, we discussed the detailed signaling cascades via membrane transporters that confer plant tolerance to abiotic stresses and possible significant use in plant development for climate-resilient crops. Plant transporters play significant roles in nutrient uptake, cellular balance, and stress responses. They facilitate the exchange of chemicals and signals across the plant's membrane by signal transduction, osmotic adjustment, and ion homeostasis. Therefore, research into plant transporters is crucial for understanding the mechanics of plant stress tolerance. Transporters have potential applications in crop breeding for increased stress resistance. We discuss new results about various transporter families (ABC, MATE, NRAMP, NRT, PHT, ZIP), including their functions in abiotic stress tolerance and plant development. Furthermore, we emphasize the importance of transporters in plant responses to abiotic stresses such as drought, cold, salt, and heavy metal toxicity, low light, flooding, and nutrient deficiencies. We discuss the transporter pathways and processes involved in diverse plant stress responses. This review discusses recent advances in the role of membrane transporters in abiotic stress tolerance in Arabidopsis and other crops. The review contains the genes discovered in recent years and associated molecular mechanisms that improve plants' ability to survive abiotic stress and their possible future applications by integrating membrane transporters with other technologies.

Integrative omics analyses of tea (Camellia sinensis) under glufosinate stress reveal defense mechanisms: A trade-off with flavor loss

Extensively applied glufosinate (GLU) will trigger molecular alterations in nontarget tea plants (Camellia sinensis), which inadvertently disturbs metabolites and finally affects tea quality. The mechanistic response of tea plants to GLU remains unexplored. This study investigated GLU residue behavior, the impact on photosynthetic capacity, specialized metabolites, secondary pathways, and transcript levels in tea seedlings. Here, GLU mainly metabolized to MPP and accumulated more in mature leaves than in tender ones. GLU catastrophically affected photosynthesis, leading to leaf chlorosis, and decreased Fv/Fm and chlorophyll content. Physiological and biochemical, metabolomics, and transcriptomics analyses were integrated. Showing that GLU disrupted the photosynthetic electron transport chain, triggered ROS and antioxidant system, and inhibited photosynthetic carbon fixation. GLU targeted glutamine synthetase (GS) leading to the accumulation of ammonium and the inhibition of key umami L-theanine, causing a disorder in nitrogen metabolism, especially for amino acids synthesis. Interestingly, biosynthesis of primary flavonoids was sacrificed for defensive phenolic acids and lignin formulation, leading to possible losses in nutrition and tenderness in leaves. This study revealed the defense intricacies and potential quality deterioration of tea plants responding to GLU stress. Valuable insights into detoxification mechanisms for non-target crops post-GLU exposure were offered.

Molecular mechanisms underlying coordinated responses of plants to shade and environmental stresses

Shade avoidance syndrome (SAS) is triggered by a low ratio of red (R) to far-red (FR) light (R/FR ratio), which is caused by neighbor detection and/or canopy shade. In order to compete for the limited light, plants elongate hypocotyls and petioles by deactivating phytochrome B (phyB), a major R light photoreceptor, thus releasing its inhibition of the growth-promoting transcription factors PHYTOCHROME-INTERACTING FACTORs. Under natural conditions, plants must cope with abiotic stresses such as drought, soil salinity, and extreme temperatures, and biotic stresses such as pathogens and pests. Plants have evolved sophisticated mechanisms to simultaneously deal with multiple environmental stresses. In this review, we will summarize recent major advances in our understanding of how plants coordinately respond to shade and environmental stresses, and will also discuss the important questions for future research. A deep understanding of how plants synergistically respond to shade together with abiotic and biotic stresses will facilitate the design and breeding of new crop varieties with enhanced tolerance to high-density planting and environmental stresses.

Effect of Shading on Physiological Attributes and Proteomic Analysis of Tea during Low Temperatures

Shading is an important technique to protect tea plantations under abiotic stresses. In this study, we analyzed the effect of shading (SD60% shade vs. SD0% no-shade) on the physiological attributes and proteomic analysis of tea leaves in November and December during low temperatures. The results revealed that shading protected the tea plants, including their soil plant analysis development (SPAD), photochemical efficiency (Fv/Fm), and nitrogen content (N), in November and December. The proteomics analysis of tea leaves was determined using tandem mass tags (TMT) technology and a total of 7263 proteins were accumulated. Further, statistical analysis and the fold change of significant proteins (FC < 0.67 and FC > 1.5 p < 0.05) revealed 14 DAPs, 11 increased and 3 decreased, in November (nCK_vs_nSD60), 20 DAPs, 7 increased and 13 decreased, in December (dCK_vs_dSD60), and 12 DAPs, 3 increased and 9 decreased, in both November and December (nCK_vs_nSD60). These differentially accumulated proteins (DAPs) were dehydrins (DHNs), late-embryogenesis abundant (LEA), thaumatin-like proteins (TLPs), glutathione S-transferase (GSTs), gibberellin-regulated proteins (GAs), proline-rich proteins (PRPs), cold and drought proteins (CORA-like), and early light-induced protein 1, which were found in the cytoplasm, nucleus, chloroplast, extra cell, and plasma membrane, and functioned in catalytic, cellular, stimulus-response, and metabolic pathways. In conclusion, the proliferation of key proteins was triggered by translation and posttranslational modifications, which might sustain membrane permeability in tea cellular compartments and could be responsible for tea protection under shading during low temperatures. This study aimed to investigate the impact of the conventional breeding technique (shading) and modern molecular technologies (proteomics) on tea plants, for the development and protection of new tea cultivars.

Physiological, Photosynthetic, and Transcriptomics Insights into the Influence of Shading on Leafy Sweet Potato

Leafy sweet potato is a new type of sweet potato, whose leaves and stems are used as green vegetables. However, sweet potato tips can be affected by pre-harvest factors, especially the intensity of light. At present, intercropping, greenhouse planting, and photovoltaic agriculture have become common planting modes for sweet potato. Likewise, they can also cause insufficient light conditions or even low light stress. This research aimed to evaluate the influence of four different shading levels (no shading, 30%, 50%, and 70% shading degree) on the growth profile of sweet potato leaves. The net photosynthetic rate, chlorophyll pigments, carbohydrates, and polyphenol components were determined. Our findings displayed that shading reduced the content of the soluble sugar, starch, and sucrose of leaves, as well as the yield and Pn. The concentrations of Chl a, Chl b, and total Chl were increased and the Chl a/b ratio was decreased for the more efficient interception and absorption of light under shading conditions. In addition, 30% and 50% shading increased the total phenolic, total flavonoids, and chlorogenic acid. Transcriptome analysis indicated that genes related to the antioxidant, secondary metabolism of phenols and flavonoids, photosynthesis, and MAPK signaling pathway were altered in response to shading stresses. We concluded that 30% shading induced a high expression of antioxidant genes, while genes related to the secondary metabolism of phenols and flavonoids were upregulated by 50% shading. And the MAPK signaling pathway was modulated under 70% shading, and most stress-related genes were downregulated. Moreover, the genes involved in photosynthesis, such as chloroplast development, introns splicing, and Chlorophyll synthesis, were upregulated as shading levels increased. This research provides a new theoretical basis for understanding the tolerance and adaptation mechanism of leafy sweet potato in low light environments.