Editors' ChoicePlant biology

Decap to Form Veins

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Science's STKE  03 Jul 2007:
Vol. 2007, Issue 393, pp. tw237
DOI: 10.1126/stke.3932007tw237

The balance between synthesis and decay controls protein abundance at multiple levels. Goeres et al. found that a specific 5′→3′ mRNA degradation pathway involving an mRNA decapping complex was crucial for seedling development in Arabidopsis thaliana. The phenotypes of mutants in the VCS and TDT genes were similar, with defective leaf formation with vein defects, short roots with swollen root hairs, and short swollen hypocotyls. Confocal microscopy revealed that the shoot apical meristem cells were disorganized in the vcs-7 and tdt-1 plants and that leaf primordia were absent in seedlings that were 3 days old, which is when the leaf primordia appear in wild-type plants. Reporter gene analysis for vascular tissue and precursors suggested that the tdt-1 mutant vascular phenotype arose as a consequence of defective formation of the provascular cell specification, which is controlled by auxin signaling, in the hypocotyl to cotyledon transition zone. Cloning revealed that TDT encoded a protein homologous to yeast and mammalian DCP2, a NUDIX and muT-domain containing mRNA decapping enzyme. VCS, which interacted with TDT in a yeast two-hybrid assay, appeared to be important for localizing TDT to cytoplasmic P-bodies, which are the sites of mRNA decapping and degradation. In vcs-7 mutants, localization of a green fluorescent protein (GFP) TDT fusion protein to cytoplasmic foci with characteristics of P-bodies was lost. Analysis of specific mRNAs, as well as microarray analysis, indicated that TDT and VCS were involved in controlling mRNA abundance. However, not all mRNAs exhibited decreased decay rates, suggesting that this particular mRNA decay pathway was specific to a subset of transcripts. The transcripts that did accumulate in the mutants exhibited the presence of the 5′ cap, consistent with VCS and TDT as constituents of the decapping pathway.

D. C. Goeres, J. M. Van Norman, W. Zhang, N. A. Fauver, M. L. Spencer, L. E. Sieburth, Components of the Arabidopsis mRNA decappng complex are required for early seedling development. Plant Cell 19, 1549-1564 (2007). [Abstract] [Full Text]

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