Wall-associated kinase GhWAK13 mediates arbuscular mycorrhizal symbiosis and Verticillium wilt resistance in cotton

Glutamine synthetase GhGLN1.5 regulates arbuscular mycorrhizal symbiosis and Verticillium wilt resistance in cotton by modulating inorganic nitrogen assimilation

Arbuscular mycorrhizal (AM) fungi play a crucial role in the nitrogen uptake and Verticillium wilt resistance of cotton. The absorbed inorganic nitrogen is converted into organic nitrogen through nitrogen assimilation mediated by glutamine synthetase (GS). However, the role of GS in AM symbiosis and Verticillium wilt resistance remains unclear. We identified an AM fungus-induced GS gene, GhGLN1.5, which participated in AM symbiosis. Both in vivo and in vitro analyses demonstrated that GhGLN1.5 exhibits catalytic activity of GS. The knockdown of GhGLN1.5 resulted in a reduction of AM colonization, nitrogen uptake capacity, and AM symbiosis-dependent resistance to Verticillium wilt. Heterologous expression of GhGLN1.5 enhanced AM symbiosis, increased GS activity, and promoted plant growth. The knockout of GhGLN1.5 in cotton inhibited AM symbiosis. Furthermore, we identified an AM fungus-induced ethylene response factor gene GhWRI3 through yeast one-hybrid library screening and found that GhWRI3 activates the expression of GhGLN1.5 via AW-box element. These findings provide valuable insights into the molecular mechanisms of GhGLN1.5 expression in AM symbiosis, nitrogen assimilation, and Verticillium wilt resistance in cotton, suggesting potential strategies for regulating AM symbiosis in cotton through the WRI3-GLN1.5 module.

Characterization of the wall-associated kinase (WAK) gene family in Gossypium barbadense reveals the positive role of GbWAK5 in salt tolerance

KEY MESSAGE

We characterized the WAK gene family in Gossypium barbadense and revealed the potential function of GbWAK5 in regulating salt tolerance by modulating ion homeostasis. Soil salinization is one of the main factors restricting cotton production. Although the role of the wall-associated kinases (WAKs) in plants has been extensively studied, its response to salt stress in sea-island cotton (Gossypium barbadense L.) has not been reported. Here, we conducted a whole-genome analysis of the WAK gene family in G. barbadense, identifying a total of 70 GbWAK genes, which were classified into five clades. Segmental and tandem duplication events have contributed to the expansion of the GbWAK gene family. A large number of cis-acting elements were predicted in the GbWAK promoter region. Through RNA sequencing, 37 GbWAKs that potentially play a role in cotton's response to salt stress were screened out, among which 10 genes with sustained up-regulated expression were confirmed by quantitative real-time PCR (qRT-PCR). GbWAK5, a member of Clade II, was significantly up-regulated following NaCl treatment and exhibited a typical WAK structure. Subcellular localization indicated that GbWAK5 is localized on the plasma membrane. Virus-induced gene silencing (VIGS) experiments revealed that the knockdown of GbWAK5 resulted in more severe dehydration and wilting in plants compared to the control under NaCl treatment. RNA-seq analysis revealed that several ion transport-related genes were down-regulated in TRV:GbWAK5 plants under salt stress, while TRV:GbWAK5 plants accumulated more Na+ and exhibited a higher Na+/K+ ratio compared to TRV:00 plants. These results offer a comprehensive analysis of the G. barbadense WAK gene family for the first time, and conclude that GbWAK5 is a promising gene for improving cotton's resistance to salt stress.

Comparative Transcriptome Analysis of Gossypium hirsutum Mutant (xin w 139) and Wild-Type (Xin W 139) Plants During Seed Embryo Development

BACKGROUND

Cotton seeds are the main byproduct of cotton crops. The phenomenon of plants failing to develop mature and full seeds is called seed embryo abortion, which leads to a decrease in seed yield and potentially causes economic losses.

METHODS

We report a phenotypic evaluation of seed embryos from G. hirsutum mutant (xin w 139) and wild-type (Xin W 139) lines and a comparative RNA-seq study at four developmental stages.

RESULTS

The field results from two years showed that the sterility rate and malformation rate of xin w 139 were significantly lower than those of Xin W 139, and the RNA-seq data revealed that the differences in the development of the seed embryos of the two lines mainly occurred after 20 days post anthesis (DPA). Differential analysis revealed a total of 29,151 differentially expressed genes (DEGs), including 2696 transcription factors (TFs), between the two lines, in which the fatty acid and glucose metabolism-related pathways were significantly enriched. These DEGs were divided into 8 clusters, with the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of each cluster being annotated. Furthermore, a gene regulatory network was built using weighted correlation network analysis (WGCNA), revealing 9 key genes that play crucial roles in shaping the developmental disparities of seed embryos between the two lines, among which 3 are TFs.

CONCLUSIONS

These findings offer a foundational framework for comprehending the molecular mechanisms underlying cottonseed embryo development, as well as presenting novel genetic reservoirs for further investigations into cottonseed embryo development.

Breaking barriers: improving time and space resolution of arbuscular mycorrhizal symbiosis with single-cell sequencing approaches

The cell and molecular bases of arbuscular mycorrhizal (AM) symbiosis, a crucial plant-fungal interaction for nutrient acquisition, have been extensively investigated by coupling traditional RNA sequencing techniques of roots sampled in bulk, with methods to capture subsets of cells such as laser microdissection. These approaches have revealed central regulators of this complex relationship, yet the requisite level of detail to effectively untangle the intricacies of temporal and spatial development remains elusive.The recent adoption of single-cell RNA sequencing (scRNA-seq) techniques in plant research is revolutionizing our ability to dissect the intricate transcriptional profiles of plant-microbe interactions, offering unparalleled insights into the diversity and dynamics of individual cells during symbiosis. The isolation of plant cells is particularly challenging due to the presence of cell walls, leading plant researchers to widely adopt nuclei isolation methods. Despite the increased resolution that single-cell analyses offer, it also comes at the cost of spatial perspective, hence, it is necessary the integration of these approaches with spatial transcriptomics to obtain a comprehensive overview.To date, few single-cell studies on plant-microbe interactions have been published, most of which provide high-resolution cell atlases that will become crucial for fully deciphering symbiotic interactions and addressing future questions. In AM symbiosis research, key processes such as the mutual recognition of partners during arbuscule development within cortical cells, or arbuscule senescence and degeneration, remain poorly understood, and these advancements are expected to shed light on these processes and contribute to a deeper understanding of this plant-fungal interaction.

Walking on a tightrope: cell wall-associated kinases act as sensors and regulators of immunity and symbiosis

This article is a Commentary on Zhang et al. (2024), 242: 2180–2194.

The role of VdSti1 in Verticillium dahliae: insights into pathogenicity and stress responses

Sti1/Hop, a stress-induced co-chaperone protein, serves as a crucial link between Hsp70 and Hsp90 during cellular stress responses. Despite its importance in stress defense mechanisms, the biological role of Sti1 in Verticillium dahliae, a destructive fungal pathogen, remains largely unexplored. This study focused on identifying and characterizing Sti1 homologues in V. dahliae by comparing them to those found in Saccharomyces cerevisiae. The results indicated that the VdSti1-deficient mutant displayed increased sensitivity to drugs targeting the ergosterol synthesis pathway, leading to a notable inhibition of ergosterol biosynthesis. Moreover, the mutant exhibited reduced production of microsclerotia and melanin, accompanied by decreased expression of microsclerotia and melanin-related genes VDH1, Vayg1, and VaflM. Additionally, the mutant's conidia showed more severe damage under heat shock conditions and displayed growth defects under various stressors such as temperature, SDS, and CR stress, as well as increased sensitivity to H2O2, while osmotic stress did not impact its growth. Importantly, the VdSti1-deficient mutant demonstrated significantly diminished pathogenicity compared to the wild-type strain. This study sheds light on the functional conservation and divergence of Sti1 homologues in fungal biology and underscores the critical role of VdSti1 in microsclerotia development, stress response, and pathogenicity of V. dahliae.