Tomato (Solanum lycopersicum L.) YTH Domain-Containing RNA-Binding Protein (YTP) Family Members Participate in Low-Temperature Treatment and Waterlogging Stress Responses

YT521-B homology (YTH) domain-containing RNA-binding proteins (YTPs) are important N6-methyladenosine (m6A) readers that have crucial roles in determining the destiny of m6A-modified RNAs, which are the most widespread RNA modifications in eukaryotes. Tomatoes (Solanum lycopersicum L.) hold significant importance in both dietary consumption patterns and scientific inquiries. While the YTP gene family has been characterized in tomatoes, their specific reactions to the low temperature and waterlogging stresses remain to be elucidated. In our study, nine tomato SlYTPs could be divided into five subclasses, YTHDFa-c and YTHDCa-b. After gene cloning and measuring their expression levels under stress conditions, it was revealed that SlYTP8 exhibited increased sensitivity to low-temperature treatment, while the expression levels of SlYTP9 were notably upregulated in leaf tissues subjected to waterlogging conditions. As members of the YTHDFc subfamily, SlYTP8 and SlYTP9 are both localized in the cytoplasm. Nevertheless, overexpression (OE) of SlYTP8 increased the sensitivity of tomato plants to low-temperature treatment, which was manifested by a higher accumulation of malondialdehyde (MDA) and hydrogen peroxide (H2O2) and a weaker reactive oxygen species scavenging ability compared to wild-type (WT) tomatoes. However, in comparison to WT plants, the leaves of SlYTP9 OE tomatoes showed higher chlorophyll content and a stronger reactive oxygen species scavenging ability after 3 days of waterlogging treatment, thereby increasing the resistance of tomatoes to waterlogging stress. Moreover, in order to investigate the possible molecular mechanisms underlying their responses to the low temperature and waterlogging stresses, the transcription factors and interacting protein networks associated with SlYTP8/9 promoters and proteins were also predicted, respectively. These results could fill the gap in the understanding of tomato YTPs in response to the low temperature and waterlogging stresses, while also providing a theoretical and experimental basis for subsequent studies on their molecular mechanisms.