Overexpression of auxin early response gene LcSAUR1 (Leymus chinensis) increases sensitivity to alkali and drought stresses in Arabidopsis and rice.

Alkali and drought stresses are two common abiotic factors affecting plants growth and development. Auxin signal also regulates plant responses to abiotic stresses. Especially, auxin early response genes can quickly respond after sensing auxin signal. However, auxin early response genes related to alkali and drought stresses are rarely reported in Leymus chinensis. In this study, LcSAUR1 (small auxin-up RNA) was isolated from the difference expression analysis of the transcriptome data in Leymus chinensis under alkali and drought stresses. And LcSAUR1 exhibited inhibitory expression under alkali and drought stresses. Further research showed that LcSAUR1 was localized in the nucleus, cell membrane, and chloroplast, suggesting that it might has special biofunction. Overexpression of LcSAUR1 led to shorter root lengths in LcSAUR1-transgenic Arabidopsis and rice. Under alkali and drought stresses, the OE-LcSAUR1-Col lines showed delayed germination and larger stomatal aperture, and the OE-LcSAUR1-NIP lines had lower survival rates. The determination of physiological indicators including hydrogen peroxide (H2O2), malondialdehyde (MDA), catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), the contents of proline (PRO), and the staining of nitro-blue tetrazolium (NBT) and Diaminobenzidine (DAB) indicated that the overexpressed LcSAUR1-transgenic Arabidopsis and rice produced more reactive oxygen species (ROS). In addition, for the genes related to abiotic stresses, the expression of AtSnRK2.6, AtNCEB3, AtCAT2, and AtAPX1 in the OE-LcSAUR1-Col lines, and OsLEA3-2, OsABF1, OsCAT2, and OsAPX2 in the OE-LcSAUR1-NIP lines were all lower than their WT under alkali and drought stresses, suggesting that LcSAUR1 regulates alkali and drought tolerances might through those abiotic-related genes. The study suggests that the LcSAUR1 negatively regulates alkali and drought stresses, providing a novel insight into auxin signal and abiotic stresses.