The Plant Journal最新文献

Drought poses a critical threat to global agriculture, food security, and livestock sustainability. In Brassica napus L. (B. napus), a major oilseed crop, yield losses under water deficit underscore the urgent need for breeding strategies that improve water-use efficiency. Here, this study demonstrates that CIPK9 loss-of-function lines of B. napus displayed enhanced drought tolerance compared with the wild-type (WT). Yeast two-hybrid, split-luciferase complementation (LCI), and bimolecular fluorescence complementation (BiFC) assays showed that BnaCIPK9 physically interacts with PP2C39 both in vivo and in vitro. Transcript analysis and enzymatic assays further revealed that CIPK9 functioned in an abscisic acid (ABA)-dependent pathway regulating ABA biosynthesis and enhanced antioxidant capacity by promoting reactive oxygen species (ROS) scavenging. In Arabidopsis, both pp2c39 and cipk9 mutants exhibited stronger drought tolerance than WT plants. Notably, cipk9 mutants showed greater detoxification capacity, resulting in reduced ROS accumulation, higher stomatal conductance, and increased growth, whereas pp2c39 mutants triggered hyperactive stress signaling, leading to elevated ROS levels, lower stomatal conductance, and growth inhibition. These findings highlight a dual drought-response strategy that balances stress defense with cellular homeostasis to sustain growth. Specifically, PP2C39 mediates ABA-induced stress signaling, while the PP2C39–CIPK9 module mitigates its cytotoxic consequences, and their interaction links two distinct pathways to maintain equilibrium between defense and growth. This work provides mechanistic insights for breeding, suggesting that exploiting functional redundancy can reduce excessive self-regulation to improve stress resilience while avoiding modifications that overactivate stress responses and compromise plant development.

Plant innate immune response is a well-balanced process with positive and negative regulations for the plants to survive. Calcium signaling is essential for pathogen-associated molecular pattern (PAMP)-driven respiratory burst oxidase homolog D (RBOHD)-mediated reactive oxygen species (ROS) burst. We show that calcium sensors calcineurin B like protein 1 (CBL1) and CBL9 and their interacting protein kinase CIPK6 negatively regulate RBOHD activity and immune response in Arabidopsis thaliana. Arabidopsis mutant cbl1cbl9, like cipk6, exhibited enhanced resistance and ROS production when infected with the bacterial pathogen Pseudomonas syringae pv. tomato (Pst). CBL1 and CBL9 enhanced kinase activity of CIPK6. CBL1/9-CIPK6 module interacts with RBOHD at the plasma membrane. CIPK6 along with CBL1 reduces RBOHD activity in planta. CIPK6 phosphorylates the N-terminal cytoplasmic domain of RBOHD at a non-conserved (S³³) and a conserved (S³⁹) serine residue. While S³⁹ phosphorylation increased RBOHD activity, S³³ phosphorylation drastically reduced it and superseded the effect of S³⁹ phosphorylation. We propose a model that CIPK6 phosphorylates RBOHD at S³³ to suppress its activity to balance ROS generation in post-PTI situation in Arabidopsis. Our study reports a direct mechanism of negative regulation of ROS production and plant immune response by a calcium-signaling module in Arabidopsis thaliana.

Protein phosphorylation has pivotal roles in ABA and dehydration stress signaling in higher plants. However, little is known about MITOGEN-ACTIVATED PROTEIN KINASE KINASE KINASE KINASE (MAP4K) in dehydration tolerance. Here, we report MAP4K1 and MAP4K2 are involved in dehydration tolerance. Mutations in MAP4K1 or MAP4K2 did not show obvious phenotype whereas map4k1 map4k2 double mutant exhibited the dwarf phenotype and low dehydration tolerance with hyposensitivity to exogenous abscisic acid. MAP4K1 and MAP4K2 interacted with SnRK2.2, SnRK2.3, and OST1 in vitro and in vivo. OST1, but not SnRK2.2 or SnRK2.3, phosphorylated MAP4K1 and MAP4K2. Mass spectrometry and phosphorylation activity assay revealed that OST1 phosphorylated MAP4K1 on serine 487 and MAP4K2 on serine 488, respectively. MAP4K1 and MAP4K2 as well as OST1 act in the same dehydration stress pathway, with OST1 acting downstream of MAP4K1 and MAP4K2. Together, we identified MAP4K1 and MAP4K2 as new substrates of OST1, and MAP4K1 and MAP4K2 are redundant in dehydration tolerance.

The transcription factor WIP2/NO TRANSMITTING TRACT (WIP2/NTT) belongs to the WIP zinc finger family. Loss of WIP/NTT function in Arabidopsis thaliana causes alterations in specific tissues in the gynoecium. It also impairs root development, but only when combined with the loss of WIP4 and WIP5 function, due to redundancy. Certain mutant loss-of-function phenotypes can be recovered by cytokinin application, NTT interacts with cytokinin signaling components, and the phenotypes displayed by plants with increased WIP2/NTT expression also suggest a possible interaction with this pathway. Therefore, the objective of this study was to investigate the relationship between WIP2/NTT and the cytokinin pathway. To overcome the issue of genetic redundancy, we used a commonly used inducible system. We found that WIP2/NTT induction alters cytokinin levels and signaling in a tissue-specific manner, as shown by cytokinin content measurements and TCSn::GFP reporter analysis. Transcriptome analyses revealed candidate target genes related to the cytokinin pathway. Yeast one-hybrid and transactivation assays demonstrated direct NTT binding to regulatory regions of the cytokinin genes ISOPENTENYL TRANSFERASE 5 (IPT5), ARABIDOPSIS HISTIDINE PHOSPHOTRANSFER PROTEIN 6 (AHP6), and CYTOKININ OXIDASE/DEHYDROGENASE 7 (CKX7) involved in cytokinin biosynthesis, signaling, and degradation, respectively. Moreover, immunolocalization assays revealed that cytokinin distribution was altered in loss of function mutants and after NTT induction. The results of this work indicate that WIP2/NTT modulates cytokinin homeostasis.

A well-developed root system is one of the morphological mechanisms through which xerophytes adapt to drought. However, the molecular mechanisms underlying root growth are not completely known. In this work, two domain of unknown function 707 (DUF707) proteins were identified as hub genes for the response of roots to drought stress in Lespedeza potaninii, a xerophytic subshrub. We found that angiosperm DUF707 proteins can be divided into two subfamilies. LpDUF707-1 expression was strongly induced under drought stress and abscisic acid (ABA) treatment in the roots of L. potaninii, and its promoter activity in the roots was significantly induced by drought stress and mannitol treatments. The overexpression of LpDUF707-1 significantly improved root growth and drought tolerance, whereas the silencing of LpDUF707-1 inhibited root growth and reduced drought tolerance. We further revealed that the LpOBP3.1 transcription factor directly binds to the promoter region of LpDUF707-1, thereby repressing its activity. LpOBP3.1 expression was strongly suppressed under drought stress and ABA treatment in the roots of L. potaninii. The overexpression of LpOBP3.1 significantly inhibited root growth and decreased drought tolerance, whereas LpOBP3.1-RNAi lines presented the opposite pattern. Collectively, our results demonstrated that this novel module regulates root growth and drought tolerance in L. potaninii, thus providing gene targets for the development of elite crop varieties with well-developed root-mediated drought tolerance.

Future climatic conditions are projected to become warmer and drier, critically challenging tree growth and survival. Understanding how photosynthesis and respiration of tree seedlings acclimate to warming is pivotal for predicting seedling responses to climate change and tree carbon dynamics. However, the photosynthetic capacity parameters of thermal acclimation remain unresolved; particularly their interaction with water availability constraints and local climate adaptation needs to be fully explored. Here, we grew seedlings of a widely planted timber species in subtropical China, Pinus massoniana, with two provenances from contrasting climates of origin (cooler-drier and warmer-wetter), under three growth temperatures (22°C, 26°C, and 30°C) and two water conditions (well-watered and drought). Temperature responses of gas exchange and nutrient status were investigated, together with a data synthesis of meta-analysis. The experimental results showed that under well-watered conditions, the optimal temperature for photosynthesis (T_optA), the net photosynthetic rate (A₂₅) and dark respiration rate (R₂₅) at 25°C, and respiratory sensitivity parameters (Q₁₀) remained unexpectedly stable under warming for both provenances, contrasting with our hypotheses; however, data synthesis shows that the T_optA from the cooler region increased with warming. Drought reduced T_optA and A₂₅, largely related to the magnitude of warming. Compared to drought-only conditions, warming and drought in combination induced an increase in T_optA and the optimal temperature for photosynthetic electron transport rate (T_optJ) in the provenance from the warmer-wetter region and a reduction in Q₁₀ for both provenances, but did not affect A₂₅ and R₂₅. Collectively, our results indicated that thermal acclimation of photosynthesis and respiration in P. massoniana seedlings was limited under well-watered conditions. However, drought increased the capacity for thermal acclimation in the warmer-wetter provenance compared to the cooler-drier provenance, suggesting that P. massoniana seedlings from warmer-wetter areas may cope better with future warm and dry environments.