Down-stream components of cytokinin signaling and the role of cytokinin throughout the plant.
ABSTRACT Cytokinins constitute a class of plant hormones influencing numerous aspects of growth and development. These processes occur through the downstream components of the cytokinin signaling pathway after its perception and signal transduction. The importance of these downstream signaling components has been revealed through the use of both traditional genetic and advanced molecular approaches studying mutants and transgenic lines involving cytokinin and diverse plant growth and developmental processes. Interestingly, these effects are not always directly via cytokinin, but by interactions with other plants hormones or transcription factor cascades, which can involve regulatory loops that affect transcription as well as hormone concentrations. This review covers recent advancements in understanding the role of cytokinin via its signaling components, specifically the downstream responses regulators in controlling vital plant growth and developmental processes.
- SourceAvailable from: G. Eric Schaller[show abstract] [hide abstract]
ABSTRACT: Two-component signaling systems, involving His kinases, His-containing phosphotransfer proteins, and response regulators, have been implicated in plant responses to hormones and environmental factors. Genomic analysis of Arabidopsis supports the existence of 22 response regulators (ARRs) that can be divided into at least two distinct groups designated type-A and type-B. Phylogenetic analysis indicates that the type-B family is composed of one major and two minor subfamilies. The expression of the type-B ARRs was examined by using both reverse transcription-PCR and beta-glucuronidase fusion constructs. The major subfamily of type-B ARRs showed particularly high expression in regions where cytokinins play a significant role, including cells in the apical meristem region and in young leaves that would be undergoing cell division. 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. These data suggest that differing expression levels of the type-B ARRs may play a role in modulating the cellular responses to cytokinin.Plant physiology 07/2004; 135(2):927-37. · 6.56 Impact Factor