Search

Summary: Phytohormones possess unique chemical structures, and their physiological effects are regulated through intricate interactions or crosstalk among multiple phytohormones. MALDI‐MSI enables the simultaneous detection and imaging of multiple hormones. However, its application for tracing phytohormones is currently restricted by low abundance of hormone in plant and suboptimal matrix selection.2,4‐Dihydroxy‐5‐nitrobenzoic acid (DHNBA) was reported as a new MALDI matrix for the enhanced detection and imaging of multiple phytohormones in plant tissues. DHNBA demonstrates remarkable sensitivity improvement when compared to the commonly used matrix, 2,5‐dihydroxybenzoic acid (DHB), in the detection of isoprenoid cytokinins (trans‐zeatin (tZ), dihy‐drozeatin (DHZ), meta‐topolin (mT), and N6‐(Δ2‐isopentenyl) adenine (iP)), jasmonic acid (JA), abscisic acid (ABA), and 1‐aminocyclo‐propane‐1‐carboxylic acid (ACC) standards.The distinctive properties of DHNBA (i.e. robust UV absorption, uniform matrix deposition, negligible background interference, and high ionization efficiency of phytohormones) make it as an ideal matrix for enhanced detection and imaging of phytohormones, including tZ, DHZ, ABA, indole‐3‐acetic acid (IAA), and ACC, by MALDI‐MSI in various plant tissues, for example germinating seeds, primary/lateral roots, and nodules.Employing DHNBA significantly enhances our capability to concurrently track complex phytohormone biosynthesis pathways while providing precise differentiation of the specific roles played by individual phytohormones within the same category. This will propel forward the comprehensive exploration of phytohormonal functions in plant science. [ABSTRACT FROM AUTHOR]

In plants, anisotropic cell expansion depends on cortical microtubules that serve as tracks along which macromolecules and vesicles are transported by the motor kinesins of unknown identities. We used cotton (Gossypium hirsutum) fibers that underwent robust elongation to discover kinesins that are involved in cell elongation and found Gh KINESIN-4A expressed abundantly. The motor was detected by immunofluorescence on vesicle-like structures that were associated with cortical microtubules. In Arabidopsis thaliana, the orthologous motor At KINESIN-4A/FRA1, previously implicated in cellulose deposition during secondary growth in fiber cells, was examined by live-cell imaging in cells expressing the fluorescently tagged functional protein. The motor decorated vesicle-like particles that exhibit a linear movement along cortical microtubules with an average velocity of 0.89 μm/min, which was significantly different from those linked to cellulose biosynthesis. We also discovered that At KINESIN-4A/FRA1 and the related At KINESIN-4C play redundant roles in cell wall mechanics, cell elongation, and the axial growth of various vegetative and reproductive organs, as the loss of At KINESIN-4C greatly enhanced the defects caused by a null mutation at the KINESIN-4A/FRA1 locus. The double mutant displayed a lack of cell wall softening at normal stages of rapid cell elongation. Furthermore, enhanced deposition of arabinose-containing carbohydrate was detected in the kinesin-4 mutants. Our findings established a connection between the Kinesin-4-based transport of cargoes containing non-cellulosic components along cortical microtubules and cell wall mechanics and cell elongation in flowering plants.

Microtubule (MT)-dependent MT nucleation by γ-tubulin is required for interphase plant cells to establish a highly dynamic cortical MT network underneath the plasma membrane, which influences the deposition of cell wall materials and consequently governs patterns of directional cell expansion. Newly formed MTs either assume 40° angles or are parallel to the extant ones. To date, it has been enigmatic how the γ-tubulin complex is recruited to the sidewall of cortical MTs and initiates MT nucleation. Here, we discovered that the augmin complex was recruited to cortical MTs and initiated MT nucleation in both branching and parallel forms. The augmin complex overwhelmingly colocalized with the γ-tubulin complex. When the function of the augmin complex was compromised, MT nucleation frequency was drastically reduced, most obviously for the branching nucleation. Consequently, the augmin knockdown cells displayed highly parallel and bundled MTs, replacing the fine and mesh-like MT network in the wild-type cells. Our findings uncovered a mechanism by which the augmin complex functions in recruiting the γ-tubulin complex to cortical MTs and initiating MT nucleation, and they shifted the paradigm of the commonly perceived mitotic-specific function of augmin and established its crucial function in MT-dependent MT nucleation in interphase plant cells.

While soybean (Glycine max L.) provides the most important source of vegetable oil and protein, it is sensitive to salinity, which seriously endangers the yield and quality during soybean production. The application of Plant Growth‐Promoting Rhizobacteria (PGPR) to improve salt tolerance for plant is currently gaining increasing attention. Streptomycetes are a major group of PGPR. However, to date, few streptomycetes has been successfully developed and applied to promote salt tolerance in soybean. Here, we discovered a novel PGPR strain, Streptomyces lasalocidi JCM 3373T, from 36 strains of streptomycetes via assays of their capacity to alleviate salt stress in soybean. Microscopic observation showed that S. lasalocidi JCM 3373T does not colonise soybean roots. Chemical analysis confirmed that S. lasalocidi JCM 3373T secretes indole‐3‐carboxaldehyde (ICA1d). Importantly, IAC1d inoculation alleviates salt stress in soybean and modulates its root architecture by regulating the expression of stress‐responsive genes GmVSP, GmPHD2 and GmWRKY54 and root growth‐related genes GmPIN1a, GmPIN2a, GmYUCCA5 and GmYUCCA6. Taken together, the novel PGPR strain, S. lasalocidi JCM 3373T, alleviates salt stress and improves root architecture in soybean by secreting ICA1d. Our findings provide novel clues for the development of new microbial inoculant and the improvement of crop productivity under salt stress. Summary statement: Streptomyces lasalocidi JCM 3373T, selected from 36 species of streptomycetes, alleviates salt tolerance and shapes root architecture by secreting a metabolite‐indole‐3‐carboxaldehyde in soybean. [ABSTRACT FROM AUTHOR]

Verticillium wilt (VW) of cotton poses a serious threat to the quality and yield of cotton. Verticillium dahliae is the primary causal agent of cotton VW. Moreover, V. dahliae can infect more than 200 species of dicotyledonous plants. The fungal cell wall plays a crucial role in its growth, development and pathogenicity. However, the mechanism of cell wall synthesis in V. dahliae and its role in pathogenesis remains unclear. In this study, we identified two chitin synthase (CHS) genes VdChs5 and VdChs7 containing myosin motor-like domain (MMD) and characterized their role in virulence of V. dahliae. The results showed that the functions of VdChs5 and VdChs7 were largely redundant, and target deletion of both VdChs5 and VdChs7 in V. dahliae did not affect vegetative growth, but reduced conidial production. ΔVdChs5Chs7 deletion mutant failed to colonize and proliferate in cotton vascular tissue, and exhibited significantly reduced virulence on cotton, suggesting that VdChs5 and VdChs7 are necessary for pathogenesis. In addition, the thickness of the cell wall in ΔVdChs5Chs7 showed significantly decreased, and ΔVdChs5Chs7 mutant exhibited hypersensitivity to cell wall perturbing agents and reactive oxygen species (ROS), indicating that VdChs5 and VdChs7 play key roles in cell wall integrity. Further, host-induced gene silencing (HIGS) silenced transcripts of VdChs5 and VdChs7 in susceptible cotton (Gossypium hirsutum L. acc. TM-1) enhanced resistance to cotton VW. Taken together, our data demonstrated that VdChs5 and VdChs7 play pivotal roles in proliferation, cell wall integrity, and pathogenicity, and provided a novel strategy to improve Verticillium wilt resistance in cotton and other susceptible host plants. [ABSTRACT FROM AUTHOR]