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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.A number of studies have suggested that WRKY34 genes may be involved in pollen viability.However,it is unclear how WRKY34 affects the viability of pollen.Treatment with cold increased the expression of WRKY34 in the wild-type.Promoter-GUS analysis revealed that the expression of WRKY34 is pollen-specific.Enhanced green fluorescent protein-tagged WRKY34 was localized in the nuclei.Competition experiments and genetic analysis confirmed that pollen harboring the wrky34 allele showed higher viability than pollen with the WRKY34 allele after cold stress.Knock-down of WRKY34 gene significantly improved cold stress tolerance of mature pollen.Further functional analysis suggested that the WRKY34 transcription factor was involved in the mature pollen development regulated by pollen-specific MIKC* class of MADS-domain transcription factors under cold stress,and cold-insensitivity of mature wrky34 pollen might be partly attributable to enhanced expression of transcriptional activator CBFs in the mutants.Taken together,the WRKY34 transcription factor negatively mediates response to cold stress tolerance of mature pollen,and may be involved in CBF signal cascade in mature pollen of Arabidopsis.