Galactinol Regulates JA Biosynthesis to Enhance Tomato Cold Tolerance.

Low temperatures can inhibit plant growth and development and reduce fruit yield. This study demonstrated that the expression of from () encoding a galactinol synthase enhanced tomato cold tolerance. In -overexpressing plants, the jasmonic acid (JA) biosynthesis substrates 13-hydroperoxylinolenicacid and 12,13-epoxylinolenicacid were significantly accumulated, and the expression levels of the ethylene response factor (-7) and serine protease inhibitor () were increased. We speculated that there may be correlations among galactinol, ethylene signaling, the protease inhibitor, protease, and JA levels. The expression levels of -7 and as well as the JA content were significantly increased under exogenous galactinol treatment. Additionally, the expression of was reduced in -7-silenced plants, and SlERF4-7 was confirmed to bind to the dehydration-responsive element (DRE) of the promoter. These results suggest that is a target gene of the SlERF4-7 transcription factor. In addition, SlSPI5 interacted with cysteine protease (SlCPase), while SlCPase interacted with lipoxygenase (SlLOX5) and allene oxide synthase (SlAOS2). When was silenced, JA levels increased and plant cold tolerance was enhanced. Therefore, galactinol regulates JA biosynthesis to enhance tomato cold tolerance through the SlERF4-7-SlSPI5-SlCPase-SlLOX5/SlAOS2 model. Overall, our study provides new perspectives on the role of galactinol in the JA regulatory network in plant adaptation to low-temperature stress.