Hyper-gravity effects on the Arabidopsis transcriptome

• Published in: Physiologia plantarum Vol. 118; no. 2; pp. 221 - 231
• Main Authors: Martzivanou, Maria, Hampp, Rüdiger
• Format: Journal Article
• Language: English
• Published: Oxford, UK Munksgaard International Publishers 01.06.2003; Blackwell
• Subjects: Arabidopsis - cytology; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins; Arabidopsis thaliana; beta-Amylase - metabolism; Biological and medical sciences; Cell Wall - enzymology; Cell Wall - genetics; Cell Wall - metabolism; Centrifugation; Fructose-Bisphosphatase - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Genes, Plant; Glucose-1-Phosphate Adenylyltransferase; Glyceraldehyde-3-Phosphate Dehydrogenases - metabolism; Hydroxymethylglutaryl CoA Reductases - metabolism; Hypergravity; Metabolism; Metabolism. Physicochemical requirements; Nucleotidyltransferases - metabolism; Phenylalanine Ammonia-Lyase - metabolism; Plant physiology and development; RNA, Plant - analysis; Space life sciences; Starch - metabolism; Transcription, Genetic; Arabidopsis thaliana; Gene; Cruciferae; Dicotyledones; Angiospermae; Spermatophyta; Gene expression; Metabolism; Gravity
• ISSN: 0031-9317; 1399-3054
• DOI: 10.1034/j.1399-3054.2003.00092.x

Callus cultures of Arabidopsis thaliana (cv. Columbia) in Petri dishes were exposed to altered g‐forces by centrifugation (1–10 g). Using semi‐quantitative RT–PCR transcripts of genes coding for metabolic key enzymes (ADP‐glucose pyrophosphorylase, ADPG‐PP; β‐amylase, fructose‐1,6‐bisphosphatase, FBPase; glyceraldehyde‐P dehydrogenase, GAPDH; hydroxymethylglutaryl‐CoA reductase, HMG; phenylalanine‐ammonium‐lyase, PAL; PEP carboxylase, PEPC) were used to monitor threshold conditions for g‐number (all) and time of exposure (β‐amylase) which led to altered amounts of the gene product. Exposure to approximately 5 g and higher for 1 h resulted in altered transcript levels: transcripts of β‐amylase, PAL, and PEPC were increased, those of ADPG‐PP decreased, while those of FBPase, GAPDH, and HMG were not affected. This probably indicates a shift from starch synthesis to starch degradation and increased rates of anaplerosis (PEPC: supply of ketoacids for amino acid synthesis). In order to get more information about g‐related effects on gene expression, we used a 1‐h exposure to 7 g for a microarray analysis, using a commercial A. thaliana chip with 4105 unique annotated clusters/genes (IncyteGenomics). Transcripts of more than 200 genes were significantly increased in amount (ratio 7 g/1 g control; 21.6 and larger). They fall into several categories. Transcripts coding for enzymes of major pathways form the largest group (25%), followed by gene products involved in cellular organization and cell wall formation/rearrangement (17%), signalling, phosphorylation/dephosphorylation (12%), proteolysis and transport (10% each), hormone synthesis plus related events (8%), defense (4%), stress‐response (2%), and gravi‐sensing (2%). Many of the alterations are part of a general stress response, but some changes related to the synthesis/rearrangement of cell wall components could be more hyper‐g‐specific. We only found few gene products, which were decreased in relation to 1 g controls, and these were less significant (ratio < 21.6). We thus assume that g‐forces above a threshold of about 5 g for 1 h are sensed by plant cells in general, causing distinct metabolic responses, which obviously in part, are regulated by gene expression.