cDNA-AFLP analysis of cold-acclimated wheat plants reveals unique transcript profiles in crown tissues
Low temperature (LT) adversely affects the productivity of plants. Hence, improving the cold hardiness of crop plants is an important goal in agriculture. However, further understanding of LT tolerance mechanisms in plants is required to achieve this objective. In wheat, survival of crown tissues after exposure to below freezing temperatures during the winter determines successful crop stand establishment at the onset of spring season. Therefore, identification of differentially expressed genes in crown tissues of cold acclimated wheat plants is important as it can allow dissection of molecular mechanisms and biochemical pathways within these tissues. In this study, cDNA-AFLP global transcriptomic profiles of crown tissues cold acclimated at 6oC for 0, 2, 14, 21, 35, 42, 56 and 70 days were compared among a cold hardy winter (vrn-A1) cv. Norstar, a tender spring habit (Vrn-A1) cv. Manitou and two reciprocal near-isogenic lines derived from these two parents differing at the vernalization locus. A total of 2061 differentially expressed transcript-derived fragments (TDFs) were identified using 37 pairs of standard AFLP primer combinations, 30 of which were considered unique due to their genotypic and temporal presence or absence. The remaining TDFs showed differential expression patterns in the four genotypes. Cluster analysis of the unique TDFs revealed influence of the genetic background on expression of these TDFs. BLAST searches of 240 sequenced TDFs showed that 87% of the TDFs had similarity to genes coding for products involved in known functions such as signal transduction, RNA processing and translation, transcription, flowering, cell wall synthesis, metabolism, and protein folding. Thirty-two TDFs did not show similarity to any known genes. Quantitative real-time PCR (QPCR) analyses of these unknown TDFs validated their differential expression patterns. Characterization of their biological function will contribute to an understanding of the role of these novel genes in LT tolerance in wheat. These results suggest that crown tissues undergo a complex adaptive process by changing the expression levels of several genes that determine the level of LT tolerance.
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