ABSTRACT
The multicellular trichomes of cucumber (Cucumis sativus L.) serve as the primary defense barrier against external factors, whose impact extends beyond plant growth and development to include commercial characteristics of fruits. The aphid (Aphis gossypii Glover) is one of prominent pests in cucumber cultivation. However, the relationship between physical properties of trichomes and the aphid resistance at molecular level remains largely unexplored. Here, a spontaneous mutant trichome morphology (tm) was characterized by increased susceptibility towards aphid. Further observations showed the tm exhibited a higher and narrower trichome base, which was significantly distinguishable from that in wild-type (WT). We conducted map-based cloning and identified the candidate, CsTM, encoding a C-lectin receptor-like kinase. The knockout mutant demonstrated the role of CsTM in trichome morphogenesis. The presence of SNP does not regulate the relative expression of CsTM, but diminishes the CsTM abundance of membrane proteins in tm. Interestingly, CsTM was found to interact with CsTIP1;1, which encodes an aquaporin with extensive reports in plant resistance and growth development. The subsequent aphid resistance experiments revealed that both CsTM and CsTIP1;1 regulated the development of trichomes and conferred resistance against aphid by affecting cytoplasmic H2O2 contents. Transcriptome analysis revealed a significant enrichment of genes associated with pathogenesis, calcium binding and cellulose synthase. Overall, our study elucidates an unidentified mechanism that CsTM-CsTIP1;1 alters multicellular trichome morphology and enhances resistance against aphid, thus providing a wholly new perspective for trichome morphogenesis in cucumber.
ABSTRACT
The spines of cucumber fruit not only have important commercial value but are also a classical tissue to study cell division and differentiation modes of multicellular trichomes. It has been reported that CsTs (C-type Lectin receptor-like kinase) can influence the development of fruit spines. In this study, we took a pair of cucumber materials defined as hard (Ts, wild type) and tender spines (ts, mutant) and defined the developmental process of fruit spines as consisting of four stages (stage I to stage IV) by continuously observing by microscope and SEM. Comparisons of transcriptome profiles at different development stages of wild-type spines showed that 803 and 722 genes were upregulated in the stalk (stage II and stage III) and base (stage IV) development stages of fruit spines, respectively. The function analysis of DEGs showed that genes related to auxin polar transport and HD-ZIP transcription factor are significantly upregulated during the development of the stalk. bHLH transcription factors and cytoskeleton-related genes were significantly upregulated during the development of the base. In addition, stage III is the key point for the difference between wild-type and mutant spines. We detected 628 DEGs between wild type and mutant at stage III. These DEGs are mainly involved in the calcium signaling of the cytoskeleton and auxin polar transport. Coincidentally, we found that CsVTI11, a factor involved in auxin signal transmission, can interact with CsTs in vivo, but this interaction does not occur between CsVTI11 and Csts, further suggesting that CsTs may regulate the development of fruit spines by influencing cell polarity. These results provide useful tools to study the molecular networks associated with cucumber fruit spine development and elucidate the biological pathways that C-type Lectin receptor-like kinase plays in regulating the development of fruit spines.
