The tomato resistance gene Bs4 suppresses leaf watersoaking phenotypes induced by AvrHah1, a transcription activator-like effector from tomato-pathogenic xanthomonads

Nanofabrication of silk microneedles for high-throughput micronutrient delivery and continuous sap monitoring in plants

Biomaterials bridging the biotic-abiotic interface in plants offer the opportunity to precisely deliver agrochemicals and continuously monitor plant health, with the goals of increasing resilience to climate change, enhancing crop production and mitigating environmental impact. In this study we report the manipulation of silk fibroin assembly with inorganics nucleation at their phase front to nanomanufacture porous and hollow microneedles that can be interfaced with plants. Plant growth analysis and quantification of wounding gene expression show a non-significant systemic wounding response to the injection of silk microneedles in tomato plants. Microneedles with a hollow structure enable the systemic delivery of plant micronutrients to treat chlorosis in tomato plants and crop biofortification through transport of human micronutrients injected in the petiole and loaded into tomato fruits. Hollow microneedles also provide access to plant vasculature for sap sampling, enabling continuous monitoring and early detection of phytoaccumulation of environmental contaminants such as cadmium.

Extracellular niche establishment by plant pathogens

The plant extracellular space, referred to as the apoplast, is inhabited by a variety of microorganisms. Reflecting the crucial nature of this compartment, both plants and microorganisms seek to control, exploit and respond to its composition. Upon sensing the apoplastic environment, pathogens activate virulence programmes, including the delivery of effectors with well-established roles in suppressing plant immunity. We posit that another key and foundational role of effectors is niche establishment - specifically, the manipulation of plant physiological processes to enrich the apoplast in water and nutritive metabolites. Facets of plant immunity counteract niche establishment by restricting water, nutrients and signals for virulence activation. The complex competition to control and, in the case of pathogens, exploit the apoplast provides remarkable insights into the nature of virulence, host susceptibility, host defence and, ultimately, the origin of phytopathogenesis. This novel framework focuses on the ecology of a microbial niche and highlights areas of future research on plant-microorganism interactions.

Differential CaKAN3-CaHSF8 associations underlie distinct immune and heat responses under high temperature and high humidity conditions

High temperature and high humidity (HTHH) conditions increase plant susceptibility to a variety of diseases, including bacterial wilt in solanaceous plants. Some solanaceous plant cultivars have evolved mechanisms to activate HTHH-specific immunity to cope with bacterial wilt disease. However, the underlying mechanisms remain poorly understood. Here we find that CaKAN3 and CaHSF8 upregulate and physically interact with each other in nuclei under HTHH conditions without inoculation or early after inoculation with R. solanacearum in pepper. Consequently, CaKAN3 and CaHSF8 synergistically confer immunity against R. solanacearum via activating a subset of NLRs which initiates immune signaling upon perception of unidentified pathogen effectors. Intriguingly, when HTHH conditions are prolonged without pathogen attack or the temperature goes higher, CaHSF8 no longer interacts with CaKAN3. Instead, it directly upregulates a subset of HSP genes thus activating thermotolerance. Our findings highlight mechanisms controlling context-specific activation of high-temperature-specific pepper immunity and thermotolerance mediated by differential CaKAN3-CaHSF8 associations.