Galactinol Regulates JA Biosynthesis to Enhance Tomato Cold Tolerance

Abstract

Low temperatures can inhibit plant growth and development and reduce fruit yield. This study demonstrated that the expression of <i>AnGolS1</i> from <i>Ammopiptanthus nanus</i> (<i>A. nanus</i>) encoding a galactinol synthase enhanced tomato cold tolerance. In <i>AnGolS1</i>-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 (<i>SlERF4</i>-7) and serine protease inhibitor (<i>SlSPI5</i>) were increased. We speculated that there may be correlations among galactinol, ethylene signaling, the protease inhibitor, protease, and JA levels. The expression levels of <i>SlERF4</i>-7 and <i>SlSPI5</i> as well as the JA content were significantly increased under exogenous galactinol treatment. Additionally, the expression of <i>SlSPI5</i> was reduced in <i>SlERF4</i>-7-silenced plants, and SlERF4-7 was confirmed to bind to the dehydration-responsive element (DRE) of the <i>SlSPI5</i> promoter. These results suggest that <i>SlSPI5</i> 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 <i>SlCPase</i> 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.