A Novel Plant-Specific Family Gene, ROOT PRIMORDIUM DEFECTIVE 1, Is Required for the Maintenance of Active Cell Proliferation

Abstract

Hypocotyl segments of Arabidopsis (Arabidopsis thaliana) produce adventitious roots in response to exogenously supplied auxin. root primordium defective 1 (rpd1) is a temperature-sensitive mutant isolated on the basis of impairment in this phenomenon. This study describes further phenotypic analysis of the rpd1 mutant and isolation of the RPD1 gene. When adventitious root formation was induced from the rpd1 explants at the restrictive temperature, cell proliferation leading to root promordia formation was initiated at the same time as in wild-type explants. However, development of the root primordia was arrested thereafter in the mutant. Temperature-shift experiments indicated that RPD1 exerts its function before any visible sign of root primordium formation. The expression patterns of the auxin-responsive gene DR5:b-glucuronidase and the cytodifferentiation marker gene SCARECROW suggest that the rpd1 mutation interferes with neither axis formation nor cellular patterning at the initial stage of root primordium development. Taken together with the effect of the rpd1 mutation on callus cell proliferation, these data imply a role for RPD1 in prearranging the maintenance of the active cell proliferation during root primordium development. Positional cloning of the RPD1 gene revealed that it encodes a member of a novel protein family specific to the plant kingdom. Disruption of the RPD1 gene by a T-DNA insertion caused embryogenesis arrest at the globular to transition stages. This phenotype is consistent with the hypothesized function of RPD1 in the maintenance of active cell proliferation.The formation of adventitious and lateral roots is a typical example of de novo postembryonic organogenesis that is achieved through the elaborate regulation of cell proliferation. The process of morphogenesis common to adventitious and lateral roots can be summarized as follows. First, cell proliferation is initiated from quiescent cells in response to endogenous or external stimuli, including auxin (Boerjan et al

A plant-specific RNA-binding domain revealed through analysis of chloroplast group II intron splicing

“…Considering the RNA-binding and RNA-splicing activities of WTF1, it seems likely that most PORR/DUF860 proteins function in organellar RNA metabolism. The one prior report concerning a member of this family, rpd1 in Arabidopsis, is consistent with this view (22). The authors concluded that defects in root and embryo development in rpd1 mutants result from the failure to maintain rapid cell divisions at critical developmental stages.…”

Sequential activation of two Dof transcription factor gene promoters during vascular development in Arabidopsis thaliana

“…Histochemical staining of GUS activity was performed basically as described in [10]. When diffuse staining patterns were observed, the concentration of potassium ferricyanide in the staining solution was increased to 3 mM to prevent diffusion of the signal [16].…”

Auxin Control in the Formation of Adventitious Roots

“…The root growth defective mutants rgd1, rgd2 and rgd3 became defective after the establishment of the root apical meristem. The ROOT INITIATION DEFECTIVE S (RIDS) gene was identified as the MOR1 / GEM gene encoding a microtubuleassociated protein (Konishi and Sugiyama, 2006). The rid 2-1 mutant is recessive temperature-sensitive mutant of Arabidopsis that was isolated by screening using adventitious root formation as an index phenotype.…”