Understanding the response to cold temperature stress is relevant for both basic biology and application. Here we report on ERF105, which is a novel cold-regulated transcription factor gene of Arabidopsis that makes a significant contribution to freezing tolerance and cold acclimation. The expression of cold-responsive genes in erf105 mutants suggests that its action is linked to the CBF regulon mediating cold responses.

Key message The four phylogenetically closely related ERF102 to ERF105 transcription factors of Arabidopsis thaliana are regulated by different stresses and are involved in the response to cold stress. Abstract The ETHYLENE RESPONSE FACTOR (ERF) genes of Arabidopsis thaliana form a large family encoding plantspecific transcription factors. Here, we characterise the four phylogenetically closely related ERF102/ERF5, ERF103/ERF6, ERF104 and ERF105 genes. Expression analyses revealed that these four genes are similarly regulated by different hormones and abiotic stresses. Analyses of tissue-specific expression using promoter:GUS reporter lines revealed their predominant expression in root tissues including the root meristem (ERF103), the quiescent center (ERF104) and the root vasculature (all). All GFP-ERF fusion proteins were nuclear-localised. The analysis of insertional mutants, amiRNA lines and 35S:ERF overexpressing transgenic lines indicated that ERF102 to ERF105 have only a limited impact on regulating shoot and root growth. Previous work had shown a role for ERF105 in the cold stress response. Here, measurement of electrolyte leakage to determine leaf freezing tolerance and expression analyses of cold-responsive genes revealed that the combined activity of ERF102 and ERF103 is also required for a full cold acclimation response likely involving the CBF regulon. These results suggest a common function of these ERF genes in the response to cold stress.

22The ETHYLENE RESPONSE FACTOR (ERF) genes of Arabidopsis thaliana form a large 23 family encoding plant-specific transcription factors. Here, we characterise the four 24 phylogenetically closely related ERF102/ERF5, ERF103/ERF6, ERF104 and ERF105 25 genes. Expression analyses revealed that these four genes are similarly regulated by 26 different hormones and abiotic stresses. Analyses of tissue-specific expression using 27 promoter:GUS reporter lines revealed their predominant expression in root tissues 28 including the root meristem (ERF103), the quiescent center (ERF104) and the root 29 vasculature (all). All GFP-ERF fusion proteins were nuclear-localised. The analysis of 30 insertional mutants, amiRNA lines and 35S:ERF overexpressing transgenic lines 31 indicated that ERF102 to ERF105 have only a limited impact on regulating shoot and root 32 growth. Previous work had shown a role for ERF105 in the cold stress response. Here, 33 measurement of electrolyte leakage to determine leaf freezing tolerance and expression 34 analyses of cold-responsive genes revealed that the combined activity of ERF102 and 35 ERF103 is also required for a full cold acclimation response likely involving the CBF 36 regulon. Together, these results suggest a common function of these ERF genes in 37 regulating root architecture and the response to cold stress. 38 39