Journal of Integrative Plant Biology最新文献

Mitogen-activated protein kinase (MAPK) cascades play vital roles in regulating plant growth, development, and stress responses. Nevertheless, the complete MAPK cascade that regulates the flowering time of Arabidopsis thaliana has not been established. A MAPK module comprising MAPKKK18, MAPKK3, and MAPK1/2/7/14 accelerates flowering in Arabidopsis. Through direct interaction, MAPK1/2/7/14 phosphorylates the S²⁴ residue of NF-YB2. Phosphorylated NF-YB2 enhances the stability of the heterotrimeric CO ~ NF-YB2 ~ NF-YC3/C9 complex and the expression of FT. Accumulation of NF-YB2 significantly promotes flowering, whereas the role of NF-YB2^S24A in this process is less pronounced. Compared with the transgenic plants overexpressing MAPKKK18 in the wild-type (WT) background, the nf-yb2 plants overexpressing MAPKKK18 bolt considerably later. Taken together, the MAPKKK18-mediated signaling cascade exerts tight control over the flowering time of Arabidopsis by modulating the phosphorylation status of NF-YB2, unveiling a flexible regulatory pathway to fine-tune plant development.

Tension wood (TW), a type of reaction wood that develops in angiosperm trees in response to gravistimulation, serves as an ideal model for investigating the regulatory mechanisms underlying xylem cell differentiation and cell wall deposition. The initial biological signals that induce the formation of reaction wood in response to gravitational stimuli remain poorly understood. In this study, we utilized pharmacological and genetic approaches to modulate Ca²⁺ levels in hybrid white poplar (Populus alba × P. glandulosa) and examine the role of calcium signaling during the early stages of gravitropic responses. Our findings revealed differential cytosolic Ca²⁺ signal distribution in gravistimulated stems during the early phase of gravity induction, characterized by lower Ca²⁺ levels on the upper side (where TW forms) and higher Ca²⁺ levels on the lower side (where opposite wood forms). Consistent with this hypothesis, plants treated with LaCl₃ and those with genetically disrupted calcium channels (PagGLR3.3 knockout using the CRISPR/Cas9 system) showed reduced Ca²⁺ signals and developed characteristic TW features. These results suggest that decreased Ca²⁺ levels induce the formation of TW. Furthermore, PagGLR3.3 knockout plants with TW-like stems displayed diminished sensitivity to gravistimulation. Transcriptomic analysis revealed that the knockout of PagGLR3.3 resulted in the upregulation of genes associated with TW formation and reactive oxygen species (ROS) production. Notably, superoxide anion (O₂ ^·-) levels were significantly elevated in the cambium zone of stems subjected to gravistimulation, LaCl₃ treatment, or PagGLR3.3 knockout, indicating that reduced Ca²⁺ levels promote TW formation through increased O₂ ^·- accumulation. This study offers novel insights into the critical role of Ca²⁺ in gravitropism and TW induction in poplar.

Seed oil accumulation is an important process affecting seed quality, and regulatory factors modulating this process remain less understood, especially in soybean. In this study, through RNA-seq and gene co-expression network analysis, we identified a single MYB (Myeloblastosis)-type transcription factor GmMYB331, which promotes seed oil accumulation in soybean seeds and enhances seed size/weight as well. Transgenic soybean plants with mild GmMYB331 overexpression showed higher total fatty acid contents in seeds and higher seed yield per plant compared to the control plants. In contrast, transgenic soybean plants with strong GmMYB331 overexpression showed only increased seed size/weight but much reduced seed yield per plant, along with an altered plant architecture. Knocking out GmMYB331 by CRISPR/Cas9 produced mutants with less total fatty acids, smaller seeds, and less seed weight, indicating that the gene is required for oil accumulation and seed size/weight control. GmMYB331 may achieve these functions by differential binding to the gene promoters and activation of the downstream genes, namely, GmOLEO1/2/4 for oil accumulation in mild overexpressing plants and GmCYCD2;2 for seed size/weight increase in strong overexpressing plants. Our study reveals a possible mechanism involving differential regulation by GmMYB331 toward oil accumulation and seed size/weight increase. Manipulation of the GmMYB331 gene may facilitate breeding for high-oil and/or -yield soybean cultivars.

Rice is one of the most important food crops in the world and it is prone to attack by many diseases, such as the rice blast, sheath blight, bacterial leaf blight, and so on. These diseases represent the main constraints in rice production, threatening food security and safety. Here, new control strategies against these major rice diseases have been developed either by heterologous expression of a pathogen effector UvScd1 from false smut fungus Ustilaginoidea virens or by spraying the engineered biocontrol agent Bacillus subtilis secreting the effector UvScd1. Compared to the wild-type rice Zhonghua11 (ZH11), the rice line heterologously expressing UvScd1 showed lesion mimics and upregulated the expression of defense-related genes in leaves, including genes related to the JA and SA signaling pathways. As expected, the transgenic rice line showed broad-spectrum resistance to hemibiotrophic fungus Magnaporthe oryzae, necrotrophic fungus Rhizoctonia solani, and bacterium Xanthomonas oryzae pv. oryzae (Xoo), while there was no effect on yield-related agronomic traits compared with ZH11, suggesting that the effector UvScd1 confers both plant resistance via induction of ROS and defense-related genes, and maintains the balance between plant resistance and yield. In field experiments, comparable control efficiencies against these major rice diseases were achieved by spraying B. subtilis engineered to secrete UvScd1 and corresponding chemical pesticides, underscoring that use of biocontrol agents to secrete certain pathogen effector proteins is an effective strategy for the management of plant diseases. It is noteworthy that the application of B. subtilis engineered to secrete UvScd1 also achieved effective control for a variety of crop diseases, suggesting its excellent potential for use in practice.

Transposable elements (TEs) are essential constituents of plant genomes, promoting environmental adaptation and modulating gene expression through novel insertions. Although their activities can also trigger deleterious mutations, host mechanisms have evolved to repress them. Similarly, TEs have developed strategies to counteract silencing for their propagation. Here, the LTR retrotransposon Copia2 was identified as an active TE in japonica rice, with variations in 5-base-pair repeats within its 5'-LTR influencing promoter activity. The expression of Copia2 could be activated by drought conditions, with CG-1 motifs on LTR acting as cis-acting elements recognized by calmodulin-binding transcription activators. Under drought stress, the interaction of drought-induced proteins SCT1 and SCT2 with calmodulin OsCML4 and OsCML31 further activates Copia2 expression, enhancing its sensitivity to Ca²⁺ signaling. Additionally, decreased DNA methylation of Copia2 under drought conditions, regulated by Ca²⁺ signaling, facilitates the binding of SCT1 and SCT2 to the LTR. In summary, the drought-induced activity of Copia2 is regulated by the synergy of SCT1/SCT2 and DNA methylation mediated through Ca²⁺ signaling, potentially contributing to its recent activity in rice.

This commentary on Wang et al. (2025) and Phan et al. (2025) highlights previously undiscovered Xanthomonas pathways for nutrition acquisition, explains how Xanthomonas bacteria hijack host molecular machinery through their effector proteins, and discusses how these studies can be used to develop new disease resistance mechanisms.

Acid-producing fungal pathogens like Valsa mali enhance infectivity by secreting organic acids to acidify host environments, though the underlying cellular pH manipulation mechanisms remain unclear. Here, we identified VmAGP1 as a V. mali virulence factor whose knockout reduces virulence while heterologous expression in apples increases susceptibility. Using yeast two-hybrid (Y2H), bimolecular fluorescence complementation (BiFC), and co-immunoprecipitation (Co-IP) assays, we demonstrated that VmAGP1 interacts with apple receptor-like kinase MdLecRK2, which negatively regulates disease resistance. VmAGP1 promotes MdLecRK2 homo-dimerization, confirmed by luciferase complementation imaging (LCI) and Co-IP. Further studies reveal that MdLecRK2 interacts with and phosphorylates vacuolar H⁺-ATPase MdVHAc"1, which also negatively regulates resistance. Flow cytometry shows that VmAGP1 expression lowers intracellular pH in apple protoplasts, further decreased by MdLecRK2/MdVHAc"1 overexpression. We conclude that V. mali secretes VmAGP1 to induce MdLecRK2 homo-dimerization, triggering a phosphorylation cascade with MdVHAc"1 that acidifies apple cells to facilitate infection. This study reveals a novel pH manipulation strategy in V. mali pathogenesis, identifying potential targets for controlling Apple Valsa canker.

Seed weight is a pivotal yield-determining trait in crops, and yet, the genetic and molecular mechanisms underlying its regulation in polyploid species remain underexplored. In a previous study, we identified cqSW.A03-2, a QTL that regulates thousand seed weight (TSW) in rapeseed (Brassica napus). Here, we identify BnaA3.AHK2, encoding a histidine kinase, as the causal gene of cqSW.A03-2. BnaA3.AHK2 enhances TSW through maternal control of seed coat cell expansion without significantly compromising other yield-related traits. Protein sequence divergence between parental haplotypes caused functional differentiation, with only the ZY50 allele showing functional kinase activity and rescuing developmental defects in Arabidopsis cytokinin receptor mutants. Strikingly, BnaA3.AHK2 seems to be a cytokinin-independent operator, contrasting with the canonical cytokinin signaling pathway. Transcriptome and protein interaction analyses reveal a signaling module where BnaA3.AHK2 engages BnaAHP-BnaARR phosphorelay components to regulate downstream targets. Notably, the favorable cqSW.A03-2 haplotype has been historically selected in modern breeding, and its introgression into elite hybrids boosted TSW by 3.6%-9.1%, demonstrating its breeding value. Our findings unveil a non-canonical signaling pathway for seed size regulation, providing a strategic genetic target to break yield trade-offs in polyploid crops.