Male gametophyte-specific WRKY34 transcription factor mediates cold sensitivity of mature pollen in Arabidopsis

Abstract

Mature pollen is very sensitive to cold stress in chilling-sensitive plants. Plant WRKY DNA-binding transcription factors are key regulators in plant responses to abiotic and biotic stresses. Previous studies have suggested that WRKY34 (At4g26440) gene might be involved in pollen viability, although the mechanism involved is unclear. In this study, it is shown that cold treatment increased WRKY34 expression in the wild type, and promoter-GUS analysis revealed that WRKY34 expression is pollen-specific. Enhanced green fluorescent protein-tagged WRKY34 was localized in the nuclei. Pollen harbouring the wrky34 allele showed higher viability than pollen with the WRKY34 allele after cold treatment. Further functional analysis indicated that the WRKY34 transcription factor was involved in pollen development regulated by the pollen-specific MIKC* class of MADS-domain transcription factors under cold stress, and cold-insensitivity of mature wrky34 pollen might be partly attributable to the enhanced expression of transcriptional activator CBFs in the mutants. Thus, the WRKY34 transcription factor negatively mediated cold sensitivity of mature Arabidopsis pollen and might be involved in the CBF signal cascade in mature pollen.