High impact information on ARR2

• Ectopic expression in transgenic Arabidopsis of ARR2, the rate-limiting factor in the response to cytokinin, is sufficient to mimic cytokinin in promoting shoot meristem proliferation and leaf differentiation, and in delaying leaf senescence [1].
• Additional investigations indicate that an ETR1-initiated phosphorelay regulates the transcription factor activity of ARR2 [2].
• Analyses of loss-of-function and ARR2-overexpressing lines as well as functional assays in protoplasts indicate an important role of ARR2 in mediating ethylene responses [2].
• We identified the Arabidopsis response regulator 2 (ARR2) as a signalling component functioning downstream of ETR1 in ethylene signal transduction [2].
• A loss-of-function mutation in AHK3, but not of the other cytokinin receptors, conferred a reduced sensitivity to cytokinin in cytokinin-dependent delay of leaf senescence and abolished cytokinin-dependent phosphorylation of ARR2 [3].

Biological context of ARR2

• Cytokinin-mediated control of leaf longevity by AHK3 through phosphorylation of ARR2 in Arabidopsis [3].
• Both ARR1 and ARR2 promoted expression of a reporter gene in plant cells through their own target sequence [4].
• The genes coding for the response regulators ARR1 and ARR2 have previously been identified by in silico screening of an expression sequence tag database and subsequent cloning from both Arabidopsis cDNA and genomic libraries [4].
• Furthermore, ARR2 is transcriptionally active in yeast and binds to the promoters of nuclear genes for several components of mitochondrial respiratory chain complex I (nCI) from Arabidopsis [5].

Associations of ARR2 with chemical compounds

• Thus, the data indicate that ethylene and H(2)O(2) signalling in guard cells are mediated by ETR1 via EIN2 and ARR2-dependent pathway(s), and identify AtrbohF as a key mediator of stomatal responses to ethylene [6].

Other interactions of ARR2

• Yeast two-hybrid analysis and in vitro interaction studies suggest that ARR2 very probably forms part of a multistep two-component signalling mechanism that includes HPt proteins like AHP1 or AHP2 [5].
• This motif is highly similar to the optimal DNA-binding sites for ARR1/ARR2, type-B ARRs that have been implicated in the transcriptional elevation of the type-A ARRs [7].
• Multiple members within this same subfamily of type-B ARRs were expressed near the root tip with highest expression in the root elongation zone. beta-Glucuronidase-fusions to full-length ARR2, ARR12, and ARR19 were nuclear localized, consistent with a role in transcriptional regulation [8].
• AtARP5, AtARP6, and AtARP8 each have distinct transcript expression patterns in seedlings, roots, leaves, flowers, and siliques [9].

References