Brassica napus COL transcription factor BnCOL2 negatively affects the tolerance of transgenic Arabidopsis to drought stress

Abstract

Rapeseed (Brassica napus) is an important oil crop in the world but shows poor stress resistance. Extreme weather events, such as frequent droughts, have severely reduced rapeseed production. In recent decades, transcription factors, which are responsive to diverse stresses, have been used to explore the stress tolerance of plants by transgenic methods. In this study, we functionally characterized a member of the CONSTANS-Like transcription factor family, BnCONSTANS-LIKE2 (BnCOL2), by ectopic expression in Arabidopsis. BnCOL2 showed transcriptional activation activity and was localized in the nucleus. Tissue expression analysis showed that BnCOL2 was mainly expressed in cotyledons and leaves of rapeseed seedlings. Expression patterns indicated that BnCOL2 was induced by NaCl, PEG-6000, and abscisic acid (ABA). Overexpression of BnCOL2 in Arabidopsis resulted in mannitol- and ABA-sensitive phenotypes compared with the wild-type (WT) Arabidopsis phenotype. BnCOL2-overexpression lines exhibited significantly reduced drought stress tolerance, as illustrated by lower survival percentage and leaf temperature compared with those of the WT under drought stress. The water loss rate was remarkably reduced in BnCOL2-overexpression lines in comparison to the WT. Transcription of nine stress-responsive genes, such as AtRD29A and AtCOR27, in BnCOL2-overexpressing lines changed significantly under drought stress compared with those of the WT. The results indicate that BnCOL2 may regulate plant tolerance to drought stress by regulating expression of ABA-responsive and drought stress-related genes.