Expression of the Arabidopsis histone H2A‐1 gene correlates with susceptibility to Agrobacterium transformation

Abstract

SummaryTransformation of plant cells by Agrobacterium tumefaciens involves both bacterial virulence proteins and host proteins. We have previously shown that the Arabidopsis thaliana gene H2A-1 (RAT5), which encodes histone H2A-1, is involved in T-DNA integration into the plant genome. Mutation of RAT5 results in a severely decreased frequency of transformation, whereas overexpression of RAT5 enhances the transformation frequency (Mysore et al., 2000b). We show here that the expression pattern of RAT5 correlates with plant root cells most susceptible to transformation. As opposed to a cyclin-GUS fusion gene whose expression is limited to meristematic tissues, the H2A-1 gene is expressed in many non-dividing cells. Under normal circumstances, the H2A-1 gene is expressed in the elongation zone of the root, the region that is most susceptible to Agrobacterium transformation. In addition, when roots are incubated on medium containing phytohormones, a concomitant shift in H2A-1 expression and transformation susceptibility to the root base is observed. Inoculation of root segments with a transfer-competent, but not a transformation-deficient Agrobacterium strain induces H2A-1 expression. Furthermore, pre-treatment of Arabidopsis root segments with phytohormones both induces H2A-1 expression and increases the frequency of Agrobacterium transformation. Our results suggest that the expression of the H2A-1 gene is both a marker for, and a predictor of, plant cells most susceptible to Agrobacterium transformation.

Constitutive Expression Exposes Functional Redundancy between the Arabidopsis Histone H2A Gene HTA1 and Other H2A Gene Family Members

“…It is possible that the gene encoding histone H2A-4 (HTA4) is a pseudogene. Histone H2A-1 plays an important role in Agrobacterium-mediated transformation of Arabidopsis roots (Mysore et al, 2000b;Yi et al, 2002). The rat5 mutant contains two tandem copies of T-DNA inserted into the 39 untranslated region of the HTA1 gene.…”

“…Heterologous Histone H2A cDNAs, under the Control of a Constitutive Cauliflower Mosaic Virus 35S Promoter, Can Restore Transformation Proficiency to the rat5 Mutant It is possible that additional copies of HTA genes did not complement the rat5 mutant because these genes could not express to a sufficient extent in the root cells most susceptible to transformation by Agrobacterium (Yi et al, 2002). We therefore The 13 Arabidopsis histone H2A amino acid sequences were compared and analyzed by ClustalX (version 1.81) multiple alignment.…”

“…This mutant is resistant to Agrobacterium tumefaciens-mediated root transformation caused by a deficiency in T-DNA integration into the plant genome (Mysore et al, 2000b). More recently, we showed that this Arabidopsis HTA1 gene is expressed in nondividing tissues and that its expression is highly correlated to root cells that are most susceptible to Agrobacterium-mediated transformation (Yi et al, 2002). The expression of HTA1 in cells that are not undergoing mitotic division suggests that histone H2A-1 is a replacement histone variant.…”

Interaction of the Agrobacterium tumefaciens virulence protein VirD2 with histones

“…Several studies indicate that the chromatin structure plays an important role in AMT. Several mutations affecting the chromatin structure have been shown to affect AMT efficiency, both in plants (Mysore et al, 2000;Yi et al, 2002;Zhu et al, 2003;Tenea et al, 2009;Magori & Citovsky, 2011) and in yeast .…”

“…Knockout of the Arabidopsis thaliana RAT5 gene encoding an isoform of histone H2A was found to result in severely decreased AMT, whereas RAT5 overexpression enhanced transformation efficiency (Mysore et al, 2000). In addition, the expression pattern of RAT5 correlated with the susceptibility of plant root cells to transformation (Yi et al, 2002). Similarly, Tenea et al (2009) were able to increase susceptibility of Arabidopsis thaliana for AMT by expressing additional cDNAs encoding histones H2A (HTA), H4 (HFO) and H3-11 (HTR11) in host cells.…”