Identification and expression profiles of Tubby-like proteins coding genes in walnut (Juglans regia L.) in response to stress and hormone treatments

Tubby-like proteins (TLPs) constitute a diverse multigene family found across a broad range of eukaryotic organisms, from single-celled to multicellular eukaryotes. Despite their importance, the existence of TLPs in walnuts (Juglans regia L.) has not been reported until now. In this study, we identified 12 members of the JrTLP gene family in the walnut genome, revealing a pattern of gene replication events. Notably, all JrTLPs exhibited a split gene structure, containing two to eight introns, and these genes could be divided into five distinct categories based on their evolutionary relationships. The majority of TLP proteins possess two signature domains: the F-box and Tubby domains. Subcellular localization prediction and experiments confirmed that JrTLP2 was located in the nucleus and membrane. Expression profiling revealed that multiple JrTLPs respond to a range of stimuli, including pathogen infection, hormonal treatment (such as auxin, ABA, MeJA, and GA), and abiotic stress conditions such as cold, heat, and salt. This study represents the first comprehensive identification of the walnut TLP family, providing valuable insights into the function and regulation of TLP in walnut and laying the foundation for future functional dissection, particularly in the context of stress tolerance.