Bacterial wilt is a devastating disease of tomato (Solanum lycopersicum) caused by Ralstonia solanacearum that severely threatens tomato production. Group III WRKY transcription factors (TFs) are implicated in the plant response to pathogen infection; however, their roles in the response of tomato to R. solanacearum infection (RSI) remain largely unexplored. Here, we report the crucial role of SlWRKY30, a group III SlWRKY TF, in the regulation of tomato response to RSI. SlWRKY30 was strongly induced by RSI. SlWRKY30 overexpression reduced tomato susceptibility to RSI, and also increased H₂O₂ accumulation and cell necrosis, suggesting that SlWRKY30 positively regulates tomato resistance to RSI. RNA sequencing and reverse transcription–quantitative PCR revealed that SlWRKY30 overexpression significantly upregulated pathogenesis-related protein (SlPR-STH2) genes SlPR­STH2a, SlPR­STH2b, SlPR­STH2c, and SlPR­STH2d (hereafter SlPR­STH2a/b/c/d) in tomato, and these SlPR-STH2 genes were directly targeted by SlWRKY30. Moreover, four group III WRKY proteins (SlWRKY52, SlWRKY59, SlWRKY80, and SlWRKY81) interacted with SlWRKY30, and SlWRKY81 silencing increased tomato susceptibility to RSI. Both SlWRKY30 and SlWRKY81 activated SlPR­STH2a/b/c/d expression by directly binding to their promoters. Taking these results together, SlWRKY30 and SlWRKY81 synergistically regulate resistance to RSI by activating SlPR-STH2a/b/c/d expression in tomato. Our results also highlight the potential of SlWRKY30 to improve tomato resistance to RSI via genetic manipulations.

The loss of volatiles results in the deterioration of flavor in tomatoes. Volatiles are mainly derived from fatty acid, carotenoid, phenylpropane, and branched chain amino acids. In this study, the tomato accession CI1005 with a strong odor and accession TI4001 with a weak odor were analyzed. The volatile contents were measured in tomato fruits using gas chromatography-mass spectrometry. The scores of tomato taste and odor characteristics were evaluated according to hedonistic taste and olfaction. It was found that the content of fatty acid-derived volatiles accounted for more than half of the total volatiles that had grassy and fatty aromas. Phenylpropane-derived volatiles had irritation and floral aromas. Branched-chain amino acid-derived volatiles had a caramel aroma. Carotenoid-derived volatiles had floral, fruity, fatty, and sweet-like aromas, preferred by consumers. A lack of carotenoid-derived volatiles affected the flavor quality of tomato fruits. The accumulation of carotenoid-derived volatiles is regulated by carotenoid cleavage oxygenases (CCDs). A tissue-specific expression analysis of the SlCCD genes revealed that the expression levels of SlCCD1A and SlCCD1B were higher in tomato fruits than in other tissues. The expression levels of SlCCD1A and SlCCD1B were consistent with the trend of the carotenoid-derived volatile contents. The expression of SlCCD1A was higher than that for SlCCD1B. A bioinformatics analysis revealed that SlCCD1A was more closely linked to carotenoid metabolism than SlCCD1B. The overexpression of SlCCD1A indicated that it could cleave lycopene, α-carotene, and β-carotene to produce 6-methyl-5-hepten-2-one, geranylacetone, α-ionone, and β-ionone, increasing the floral, fruity, fatty, and sweet-like aromas of tomato fruits. The flavor quality of tomato fruits could be improved by overexpressing SlCCD1A.

Catharanthus roseus receptor-like kinase 1-like (CrRLK1L) plays pivotal roles in regulating plant growth and development, mediating intercellular signal transduction, and modulating responses to environmental stresses. However, a comprehensive genome-wide identification and analysis of the CrRLK1L gene family in maize remains elusive. In this study, a total of 24 CrRLK1L genes were identified in the maize whole genome. A phylogenetic analysis further revealed that CrRLK1L proteins from Arabidopsis, rice, and maize were grouped into nine distinct subgroups, with subgroup IV being unique to maize. Gene structure analysis demonstrated that the number of introns varied greatly among ZmCrRLK1L genes. Notably, the genome-wide duplication (WGD) events promoted the expansion of the ZmCrRLK1L gene family. Compared with Arabidopsis, there were more collinear gene pairs between maize and rice. Tissue expression patterns indicated that ZmCrRLK1L genes are widely expressed in various tissues, with ZmCrRLK1L5/9 specifically highly expressed in roots, and ZmCrRLK1L8/14/16/21/22 expressed in anthers. Additionally, RNA-seq and RT-qPCR analyses revealed that the expression of ZmCrRLK1L1/2/20/22 genes exhibited different expression patterns under drought and salt stresses. In summary, our study lays a foundation for elucidating the biological roles of ZmCrRLK1L genes in maize growth and development, reproductive development, and stress responses.