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Phospholipase C (PLC) has been implicated in several stress responses, including drought. Overexpression (OE) of PLC has been shown to improve drought tolerance in various plant species. Arabidopsis contains nine PLC genes, which are subdivided into four clades. Earlier, OE of PLC3, PLC5 or PLC7 was found to increase Arabidopsis ' drought tolerance. Here, we confirm this for three other PLCs: PLC2 , the only constitutively expressed AtPLC; PLC4 , reported to have reduced salt tolerance and PLC9 , of which the encoded enzyme was presumed to be catalytically inactive. To compare each PLC and to discover any other potential phenotype, two independent OE lines of six At PLC genes, representing all four clades, were simultaneously monitored with the GROWSCREEN-FLUORO phenotyping platform, under both control- and mild-drought conditions. To investigate which tissues were most relevant to achieving drought survival, we additionally expressed At PLC5 using 13 different cell- or tissue-specific promoters. While no significant differences in plant size, biomass or photosynthesis were found between PLC lines and wild-type (WT) plants, all PLC -OE lines, as well as those tissue-specific lines that promoted drought survival, exhibited a stronger decrease in 'convex hull perimeter' (= increase in 'compactness') under water deprivation compared to WT. Increased compactness has not been associated with drought or decreased water loss before although a hyponastic decrease in compactness in response to increased temperatures has been associated with water loss. We propose that the increased compactness could lead to decreased water loss and potentially provide a new breeding trait to select for drought tolerance. [ABSTRACT FROM AUTHOR]

The embryonic and postembryonic seedling stem, called the hypocotyl, of the model species Arabidopsis is an excellent system for studying the signal interplay in the regulation of growth and developmental responses. The current state of knowledge about the regulation of hypocotyl growth by a large repertoire of internal and external cues is presented.

GT-2 is a plant transcriptional activator that contains two separate, but similar, trihelix DNA-binding domains. GT-1 is similar to GT-2, although it contains only one of such domains, cDNAs that encode GT-2 were isolated from rice (OS-GT2) and Arabidopsis (AT-GT2). Evidence is presented for the existence of an Arabidopsis gene family that is structurally related to AT-GT2. Two members of this GT2-like family, AT-GTL1 and AT-GTL2, have been isolated and characterized. Their sequences suggest that they evolved by a recent gene duplication event. Both AT-GT2 and AT-GTL genes contain an intron in the amino-terminal trihelix motif, indicating that this DNA-binding domain resulted from exon shuffling. RNA gel blot analysis using AT-GTL1 as a probe revealed four transcripts in the aerial part of the plant. All mRNA levels were significantly higher in siliques, suggesting that this gene family may function in fruit and/or seed development. To date, DNA-binding proteins characterized by the trihelix motif have been described only in plants, and may therefore be involved in plant-specific processes. Our results show that in Arabidopsis thaliana, the trihelix motif is not restricted to the GT-1 and GT-2 DNA-binding proteins.

A study was done on the cloning, genetic mapping and expression analysis of the Arabidopsis thaliana gene. Results show the 1-aminocyclopropane-1carboxylase (ACC) synthase gene is homologous to the 5'-untranslated region with the promoter of a zucchini and tomato ACC synthase gene. Likewise, there is a conservation of seven peptide regions as well as similarity with 11 amino acids in the catalytic site of aminotransferases upon comparison with other ACC synthases.

Folate biofortified rice is recently developed as a future strategy to reduce folate deficiency, particularly in poor, rural high risk regions, like Shanxi Province. Although 62% of rice consumers in this Chinese region are likely to accept this GM product, biofortification could negatively change product attributes, which may hamper acceptance. The results of this ex-ante evaluation show that when the taste, the environmental impact or the price of folate biofortified rice would be negatively altered, the initial acceptance rate would be more or less halved. Based on a survey with 588 consumers, four different segments could be identified: 'Traditional attribute buyers' (17.9%), 'Price and availability consciousness' (20.2%), 'Intrinsic attribute buyers' (27.4%) and 'Health seekers' (34.5%). Although there is a market for folate biofortified rice in Shanxi Province, future research and development need to take into account the importance of potential attribute changes to further ensure the acceptance rate. [ABSTRACT FROM AUTHOR]

Blue-light-dependent photomorphogenesis in Arabidopsis is regulated principally by the cryptochrome flavin-type photoreceptors, which control hypocotyl growth inhibition, cotyledon and leaf expansion, and the expression of light-regulated genes. Interestingly the plant hormone cytokinin induces similar responses when added exogenously to germinating seedlings, suggesting a link between cryptochrome and cytokinin signalling pathways. In this work we explore the relationship between cryptochrome and cytokinin signalling pathways in the promotion of photomorphogenesis. The effect of exogenously added cytokinins on hypocotyl growth inhibition occurs in the dark, and is largely independent and additive to that of cryptochromes in blue light, via distinct signalling pathways. By contrast, cytokinin-dependent stimulation of anthocyanin accumulation occurs only in light, and interacts with the signalling pathway downstream of cryptochrome 1 (CRY1) at the level of transcript accumulation of anthocyanin biosynthetic genes. Mutants in elongated hypocotyl 5 ( hy5), a downstream intermediate in the CRY1 signalling pathway, show a reduced induction of anthocyanin accumulation in blue light by cytokinins, similar to that observed for cryptochrome ( cry1) mutants. Furthermore cytokinins are shown to increase levels of HY5 protein accumulation, suggesting that cytokinins may function by reducing HY5 degradation by COP1 (constitutively photomorphogenic 1). As both cryptochrome and cytokinin signalling pathways increase HY5 protein levels, and as HY5 binds to the promoters of anthocyanin biosynthetic enzymes to stimulate gene expression, it is concluded that the regulation of HY5 protein stability represents a point of convergence between cryptochrome and cytokinin signalling pathways. [ABSTRACT FROM AUTHOR]

Plants live in fixed locations and survive adversity by integrating growth responses to diverse environmental signals. Here, we show that the nuclear-localized growth-repressing DELIA proteins of Arabidopsis integrate responses to independent hormonal and environmental signals of adverse conditions. The growth restraint conferred by DELIA proteins is beneficial and promotes survival. We propose that DELLAs permit flexible and appropriate modulation of plant growth in response to changes in natural environments. [ABSTRACT FROM AUTHOR]

The stability and eventual interconversion of nine mono-glutamate folates (5-methyl-tetrahydrofolate, tetrahydrofolate, 5-formyltetrahydrofolate, 5,10-methenyltetrahydrofolate, 5,10-methylenetetrahydrofolate, dihydrofolate, 10-formylfolic acid, 10-formyltetrahydrofolate and folic acid) during the typical sample preparation steps (heat treatment for 10 min at 100 degrees C and incubation for 2 h at 37 degrees C) at different pH values have been investigated by LC-MS/MS. An LC-MS/MS method with isotopically labelled [(13)C(5)]5-methyltetrahydrofolate and [(13)C(5)] folic acid as internal standards has been developed with enhanced sensitivity using a Chromolith RP-18 column. 5-Methyltetrahydrofolate, folic acid and 10-formylfolic acid are relatively stable at different pHs (from 2 to 10) with and without heat treatment. Tetrahydrofolate shows instability at low pH. 5-Formyltetrahydrofolate and 5,10-methenyltetrahydrofolate can interconvert by changes in pH. Tetrahydrofolate and 5,10-methylenetetrahydrofolate can interconvert with formaldehyde or by changes in pH. Incubation at 37 degrees C for 2 h is much less aggressive for most folates as compared with heat treatment at 100 degrees C. At 37 degrees C most folates are stable at pH values between 4 and 8 except tetrahydrofolate and dihydrofolate, which are degraded at low pH. 10-Formyltetrahydrofolate and 5,10-methylenetetrahydrofolate cannot be quantified in the present method because these compounds are converted to 5,10-methenyltetrahydrofolate and tetrahydrofolate, respectively, in the acidic mobile phase. This study provides useful information for the analysis of folates in the future as well as for the interpretation of quantitative results from earlier work., (Copyright (c) 2007 John Wiley & Sons, Ltd.)