Sucrose transport in response to drought and salt stress involvesABA-mediated induction ofOsSWEET13andOsSWEET15in rice

Abiotic stresses, including drought and salinity, negatively affect plant development and physiology at molecular and metabolic levels. Sucrose transport, mediating distribution of photosynthates in plant, is a key physiological process impacted by drought and salinity stresses, as sucrose is a prime energy and signaling molecule as well as an osmolyte. Therefore, understanding the effects of abiotic stresses on sucrose transport and transporters, and underlying genetic and molecular mechanisms, is imperative to maintain sugar homeostasis in plants under stress. Here, we investigated the effects of drought and salinity stresses on sucrose transport and distribution, and on expression levels of genes encoding Sugars Will Eventually be Exported Transporters (SWEETs), along with a potential transcription factor regulatingSWEETexpression in rice. We observed that drought and salinity stresses increased the sucrose content in leaf and root tissues and in phloem sap of riceindicavarieties. Expression analyses ofSWEETgenes and histochemical analysis of beta-glucuronidase-reporter transgenic plants suggested that OsSWEET13 and OsSWEET15 are major SWEET transporters regulating the sucrose transport and levels in response to the abiotic stresses. Transactivation analyses showed that an abscisic acid (ABA)-responsive transcription factor OsbZIP72 directly binds to the promoters ofOsSWEET13andOsSWEET15and activates their expression. Taken together, the results showed that the higher expressions ofOsSWEET13andOsSWEET15genes, induced by binding of an ABA-responsive transcription factor OsbZIP72 to the promoters, potentially modulate sucrose transport and distribution in response to the abiotic stresses. The mechanism could possibly be targeted for maintaining sugar homeostasis in rice under drought and salinity stresses.

Automated summary

This study explored the effects of drought and salinity stresses on sucrose transport in rice, identifying OsSWEET13 and OsSWEET15 as key transporters regulating sucrose transport levels in response to stress. The ABA-responsive transcription factor OsbZIP72 directly activates the expression of OsSWEET13 and OsSWEET15, potentially modulating sucrose transport and distribution under abiotic stresses. This mechanism could be targeted for maintaining sugar homeostasis in rice under drought and salinity stresses.