The elicitor VP2 from Verticillium dahliae triggers defence response in cotton.

Verticillium dahliae is a widespread and destructive soilborne vascular pathogenic fungus that causes serious diseases in dicot plants. Here, comparative transcriptome analysis showed that the number of genes upregulated in defoliating pathotype V991 was significantly higher than in the non-defoliating pathotype 1cd3-2 during the early response of cotton. Combined with analysis of the secretome during the V991-cotton interaction, an elicitor VP2 was identified, which was highly upregulated at the early stage of V991 invasion, but was barely expressed during the 1cd3-2-cotton interaction. Full-length VP2 could induce cell death in several plant species, and which was dependent on NbBAK1 but not on NbSOBIR1 in N. benthamiana. Knock-out of VP2 attenuated the pathogenicity of V991. Furthermore, overexpression of VP2 in cotton enhanced resistance to V. dahliae without causing abnormal plant growth and development. Several genes involved in JA, SA and lignin synthesis were significantly upregulated in VP2-overexpressing cotton. The contents of JA, SA, and lignin were also significantly higher than in the wild-type control. In summary, the identified elicitor VP2, recognized by the receptor in the plant membrane, triggers the cotton immune response and enhances disease resistance.

GhWRKY41 forms a positive feedback regulation loop and increases cotton defence response against Verticillium dahliae by regulating phenylpropanoid metabolism.

Despite the established significance of WRKY proteins and phenylpropanoid metabolism in plant immunity, how WRKY proteins modulate aspects of the phenylpropanoid pathway remains undetermined. To understand better the role of WRKY proteins in plant defence, we identified a cotton (Gossypium hirsutum) protein, GhWRKY41, that is, universally and rapidly induced in three disease-resistant cotton cultivars following inoculation with the plant pathogenic fungus, Verticillium dahliae. We show that overexpression of GhWRKY41 in transgenic cotton and Arabidopsis enhances resistance to V. dahliae, while knock-down increases cotton more susceptibility to the fungus. GhWRKY41 physically interacts with itself and directly activates its own transcription. A genome-wide chromatin immunoprecipitation and high-throughput sequencing (ChIP-seq), in combination with RNA sequencing (RNA-seq) analyses, revealed that 43.1% of GhWRKY41-binding genes were up-regulated in cotton upon inoculation with V. dahliae, including several phenylpropanoid metabolism master switches, receptor kinases, and disease resistance-related proteins. We also show that GhWRKY41 homodimer directly activates the expression of GhC4H and Gh4CL, thereby modulating the accumulation of lignin and flavonoids. This finding expands our understanding of WRKY-WRKY protein interactions and provides important insights into the regulation of the phenylpropanoid pathway in plant immune responses by a WRKY protein.

Characterization of the High-Quality Genome Sequence and Virulence Factors of Fusarium oxysporum f. sp. vasinfectum Race 7.

Fusarium oxysporum f. sp. vasinfectum (Fov) is a common soilborne fungal pathogen that causes Fusarium wilt (FW) disease in cotton. Although considerable progress has been made in cotton disease-resistance breeding against FW in China, and the R gene conferring resistance to Fov race 7 (FOV) in Upland cotton (Gossypium hirsutum) has been identified, knowledge regarding the evolution of fungal pathogenicity and virulence factors in Fov remains limited. In this study, we present a reference-scale genome assembly and annotation for FOV7, created through the integration of single-molecule real-time sequencing (PacBio) and high-throughput chromosome conformation capture (Hi-C) techniques. Comparative genomics analysis revealed the presence of six supernumerary scaffolds specific to FOV7. The genes or sequences within this region can potentially serve as reliable diagnostic markers for distinguishing Fov race 7. Furthermore, we conducted an analysis of the xylem sap proteome of FOV7-infected cotton plants, leading to the identification of 19 proteins that are secreted in xylem (FovSIX). Through a pathogenicity test involving knockout mutants, we demonstrated that FovSIX16 is crucial for the full virulence of FOV7. Overall, this study sheds light on the underlying mechanisms of Fov's pathogenicity and provides valuable insights into potential management strategies for controlling FW.

Polyethyleneimine-coated MXene quantum dots improve cotton tolerance to Verticillium dahliae by maintaining ROS homeostasis.

Verticillium dahliae is a soil-borne hemibiotrophic fungal pathogen that threatens cotton production worldwide. In this study, we assemble the genomes of two V. dahliae isolates: the more virulence and defoliating isolate V991 and nondefoliating isolate 1cd3-2. Transcriptome and comparative genomics analyses show that genes associated with pathogen virulence are mostly induced at the late stage of infection (Stage II), accompanied by a burst of reactive oxygen species (ROS), with upregulation of more genes involved in defense response in cotton. We identify the V991-specific virulence gene SP3 that is highly expressed during the infection Stage II. V. dahliae SP3 knock-out strain shows attenuated virulence and triggers less ROS production in cotton plants. To control the disease, we employ polyethyleneimine-coated MXene quantum dots (PEI-MQDs) that possess the ability to remove ROS. Cotton seedlings treated with PEI-MQDs are capable of maintaining ROS homeostasis with enhanced peroxidase, catalase, and glutathione peroxidase activities and exhibit improved tolerance to V. dahliae. These results suggest that V. dahliae trigger ROS production to promote infection and scavenging ROS is an effective way to manage this disease. This study reveals a virulence mechanism of V. dahliae and provides a means for V. dahliae resistance that benefits cotton production.