Arabidopsis zinc finger homeodomain protein ZHD5 promotes shoot regeneration and confers other cytokinin-related phenotypes when overexpressed

We present the data showing that overexpression of the Arabidopsis zinc finger homeodomain protein ZHD5 promotes shoot regeneration and confers other cytokinin-associated phenotypes. To isolate protein factors that bind to the promoter element of ABF2, which is a key regulator of ABA responsive gene expression, we carried out yeast-one-hybrid screen. Four zinc finger homeodomain (ZF-HD) protein genes were identified from the screen. Expression study showed that one of the ZF-HD proteins, ZHD5, is induced by various cytokinins (CKs). We generated and analyzed ZHD5 overexpression (OX) lines to study its function. Our results revealed that ZHD5 promoted shoot regeneration efficiency significantly, obviating CK requirement. Other CK-related phenotypes, such as enhanced cell proliferation and pathogen resistance, were also observed. At the molecular level, changes in the expression levels of a number of genes relevant to the phenotypes were observed. Collectively, our results provde strong evidence that ZHD5 is involved in shoot regeneration and other aspects of CK response.