AtCPS V326M significantly affect the biosynthesis of gibberellins.

Gibberellins are a class of typical phytohormones, which regulate plant growth and development. The contents of gibberellins dramatically affect the morphology and biomass of plant. The encoding protein of copalyl diphosphate synthase gene (CPS) catalyzes the first-step in the biosynthetic pathway of gibberellins. The mutation in this gene may significantly affect the contents of gibberellins in plants. In this study, we found an EMS-triggered mutant, ga1-168, showing short roots, short hypocotyls, late flowering and dwarf. Map-based cloning revealed that the causal gene of ga1-168 was AtCPS-168, an allele of AtCPS gene. The encoding protein of AtCPS-168 was AtCPS V326M which was resulted from a single-point mutation (guanine to adenine at nucleotide 2768) of AtCPS gene. Protein domain analysis showed that V326 was located in the Terpene_synth domain. The allelism test demonstrated that AtCPS-168 was an allele of AtCPS gene. The transgenic complementation of ga1-168 indicated that AtCPS V326M led to the dwarf and bushy phenotype of ga1-168. The endogenous gibberellins contents analysis suggested that the gibberellins contents of ga1-168 were much lower than that of wild-type. The exogenous GA3 application assay uncovered that application of GA3 can complement the dwarf and bushy phenotype of ga1-168 caused by low endogenous gibberellins contents. Therefore, this study suggested that it is an elegant way to create the ideal plant architecture and height by site-directed mutating the gibberellin biosynthetic genes.

The subcellular localization and blue-light-induced movement of phototropin 1-GFP in etiolated seedlings of Arabidopsis thaliana.

Phototropin 1 (phot1) is a photoreceptor for phototropism, chloroplast movement, stomatal opening, leaf expansion, and solar tracking in response to blue light. Following earlier work with PHOT1::GFP (Sakamoto and Briggs, 2002), we investigated the pattern of cellular and subcellular localization of phot1 in 3- 4-d-old etiolated seedlings of Arabidopsis thalinana. As expressed from native upstream sequences, the PHOT1::GFP fusion protein is expressed strongly in the abaxial tissues of the cotyledons and in the elongating regions of the hypocotyl. It is moderately expressed in the shoot/root transition zone and in cells near the root apex. A fluorescence signal is undetectable in the root epidermis, root cap, and root apical meristem itself. The plasma membranes of mesophyll cells near the cotyledon margin appear labeled uniformly but cross-walls created by recent cell divisions are more strongly labeled. The pattern of labeling of individual cell types varies with cell type and developmental stage. Blue-light treatment causes PHOT1::GFP, initially relatively evenly distributed at the plasma membrane, to become reorganized into a distinct mosaic with strongly labeled punctate areas and other areas completely devoid of fluorescence--a phenomenon best observed in cortical cells in the hypocotyl elongation region. Concomitant with or following this reorganization, PHOT1::GFP moves into the cytoplasm in all cell types investigated except for guard cells. It disappears from the cytoplasm by an unidentified mechanism after several hours in darkness. Neither its appearance in the cytoplasm nor its eventual disappearance in darkness is prevented by the translation inhibitor cycloheximide, although the latter process is retarded. We hypothesize that blue-light-induced phot1 re-localization modulates blue-light-activated signal transduction.