Wenhui Sun

Gray mold caused by Botrytis cinerea poses a severe threat to tomato production. In this study, physiological, biochemical, transcriptomic, and proteomic analyses were integrated to characterize the dynamic responses of tomato ‘Ailsa Craig’ to B. cinerea infection. During B. cinerea infection, peroxidase (POD) activity showed a progressive increase, while catalase (CAT) activity was significantly upregulated at 24 hpi and remained stable through 48 hpi. Malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) contents showed a delayed response, increasing significantly only at 48 hpi, whereas SOD activity exhibited a biphasic pattern. Transcriptome and proteome profiling identified 5824 differentially expressed genes and 124 differentially expressed proteins. Functional enrichment analysis highlighted defense-related pathways, including plant–pathogen interaction, flavonoid biosynthesis, and inositol phosphate metabolism. Notably, the chlorophyll a/b-binding protein SlLhcb13 exhibited post-transcriptional upregulation despite transcriptional suppression. Functional validation demonstrated that overexpression of SlLhcb13 enhanced resistance, whereas silencing increased susceptibility. These findings identify SlLhcb13 as a positive regulator linking photosynthesis to immunity and provide new insights into the defense mechanisms of tomato.

Chloroplasts are central to plant immunity, but how the necrotrophic pathogen Botrytis cinerea (B. cinerea) manipulates chloroplast function to suppress host defences remains largely unknown. Here, we identified and characterised SlBIUPa, a B. cinerea‐induced unknown protein in tomato critical for plant response to the pathogen. Overexpression of SlBIUPa disrupts chloroplast function, while the SlBIUPa mutant increased chloroplast content, reduced photosynthesis damage, and decreased reactive oxygen species accumulation, thereby conferring remarkable resistance to B. cinerea. Mechanistically, SlBIUPa interacts with the Rubisco small subunit SlRBCS3B, inhibiting its expression and reducing Rubisco activity. Under normal conditions, the SlBIUPa is ubiquitinated and degraded via the 26S proteasome‐dependent pathway; however, B. cinerea infection attenuates this degradation, leading to SlBIUPa accumulation and increased susceptibility. Significantly, the SlBIUPa and homologue gene SlBIUPb double mutant enhanced plant resistance and increased lycopene and carotenoid content in fruits without any fitness costs. These findings offer a potential strategy for breeding tomatoes with enhanced disease resistance and improved fruit quality.

Botrytis cinerea is considered the second most important fungal plant pathogen, and can cause serious disease, especially on tomato. The TPK1b gene encodes a receptor-like kinase that can positively regulate plant resistance to B. cinerea. Here, we identified a tomato WRKY transcription factor SlWRKY3 that binds to the W-box on the TPK1b promoter. It can negatively regulate TPK1b transcription, then regulate downstream signaling pathways, and ultimately negatively regulate tomato resistance to B. cinerea. SlWRKY3 interference can enhance resistance to B. cinerea, and SlWRKY3 overexpression leads to susceptibility to B. cinerea. Additionally, we found that B. cinerea can significantly, and rapidly, induce the upregulation of SlWRKY3 expression. In SlWRKY3 transgenic plants, the TPK1b expression level was negatively correlated with SlWRKY3 expression. Compared with the control, the expression of the SA pathway marker gene PR1 was downregulated in W3-OE plants and upregulated in W3-Ri plants when inoculated with B. cinerea for 48 h. Moreover, SlWRKY3 positively regulated ROS production. Overall, SlWRKY3 can inhibit TPK1b transcription in tomato, and negatively regulate resistance to B. cinerea by modulating the downstream SA and ROS pathways.