The Arabidopsis det3 mutant reveals a central role for the vacuolar H+-ATPase in plant growth and development

Abstract

In all multicellular organisms growth and morphogenesis must be coordinated, but for higher plants, this is of particular importance because the timing of organogenesis is not fixed but occurs in response to environmental constraints. One particularly dramatic developmental juncture is the response of dicotyledonous seedlings to light. The det3 mutant of Arabidopsis develops morphologically as a light-grown plant even when it is grown in the dark. In addition, it shows organ-specific defects in cell elongation and has a reduced response to brassinosteroids (BRs). We have isolated the DET3 gene by positional cloning and provide functional and biochemical evidence that it encodes subunit C of the vacuolar H + -ATPase (V-ATPase). We show that the hypocotyl elongation defect in the det3 mutant is conditional and provide evidence that this is due to an alternative mechanism of V-ATPase assembly. Together with the expression pattern of the DET3 gene revealed by GFP fluorescence, our data provide in vivo evidence for a role for the V-ATPase in the control of cell elongation and in the regulation of meristem activity. During the development of multicellular organisms, an intricate coordination of cell division and cell enlargement is necessary to achieve both morphogenesis and growth. In contrast to our rapidly growing knowledge of pattern formation and morphogenesis in a variety of model organisms, relatively little is known about the mechanisms that control cell and organ growth and integrate it with morphogenesis. Because plants are sessile, such mechanisms are of pivotal importance as their postembryonic development takes place under a multitude of environmental constraints, including the quality and quantity of light and the availability of water and nutrients. To compensate for their lack of mobility, plants have achieved a unique plasticity of development, which allows them to adapt to their environment. Both the initiation of organs by the apical meristems, and their subsequent growth through further cell divisions and cell expansion, continue throughout the plant life cycle. Therefore, growth and morphogenesis are not only coordinated with each other, but must provide the flexibility for adaptation to suboptimal environmental conditions.One of the most striking examples for developmental plasticity in response to an environmental cue is found during early seedling development. When dicotyledenous seedlings germinate in the absence of light, morphogenesis is inhibited and growth is achieved mostly by organ-specific cell expansion. Hypocotyl cells elongate Ն100-fold of their embryonic length to position the shoot apical meristem into an environment providing light necessary to establish photoautotrophic growth. The closed cotyledons and the formation of the apical hook protect the largely inactive shoot apical meristem. Once this so-called etiolated seedling reaches the light, however, it switches to the photomorphogenetic program in which new organs develop and growth is achieved by both cell division and cell e...

The Contribution of Transposable Elements to Expressed Coding Sequence in Arabidopsis thaliana

“…These 162 genes remain expressed, and at least several are functionally well characterized: for example, DET3 (At1g12840) (Schumacher et al 1999), PGP4 (At2g47000) (Terasaka et al 2005), and HYD1 (At1g20050) (Topping et al 1997). Of the 2373 ''TE genes,'' 125 were annotated as alternatively spliced.…”

Tonoplast calcium sensors CBL2 and CBL3 control plant growth and ion homeostasis through regulating V-ATPase activity in Arabidopsis

“…As both CBL2 and CBL3 are tonoplast calcium sensors, we thus speculated that the phenotypes of cbl2 cbl3 could be attributed to the malfunction of vacuolar H + -ATPase (V-ATPase). To this end, we measured total V-ATPase activity as Concanamycin A and NO 3 − -sensitive ATP hydrolysis in microsomal membranes from rosette leaves of the wildtype, cbl2 and cbl3 single mutants, as well as cbl2 cbl3 and vha-a2 vha-a3 double mutants [34][35][36]. Compared to the wild-type control, similar levels of V-ATPase activity was found in both single mutants.…”

Cloning and Sequencing of cDNAs for Hypothetical Genes from Chromosome 2 of Arabidopsis,

“…The Arabidopsis floral homeotic mutant apetala3-1 allele is temperature sensitive and carries a mutation (from A to T) in exon 5 near the 5Ј splice site, which causes a temperature-dependent splicing defect and the mutant phenotype (Sablowski and Meyerowitz, 1998;Yi and Jack, 1998). The Arabidopsis det3-1 mutation is attributable to a T to A mutation 32 bp upstream of a putative 3Ј splice site, which causes a reduction of the transcript to approximately 50% of the wild-type level (Schumacher et al, 1999). The Arabidopsis cop1-1 allele carries a single-nucleotide change (from G to A) 4 bases upstream from the 3Ј splice site of intron 5, which results in exon skipping (Simpson et al, 1998).…”