Expression Profiling of the Arabidopsis Annexin Gene Family During Germination, De-etiolation and Abiotic Stress

Annexins are a multigene family in most plant species and are suggested to play a role in a wide variety of essential cellular processes. In Arabidopsis thaliana there are eight different annexins (AnnAt1-8), which range from 29% to 83% in deduced amino acid sequence identity. As a first step toward clarifying the individual functions of these annexins, in this study we have used quantitative real time reverse transcription PCR to assess their differential expression in different tissues or after different stimuli. We determined which annexins are expressed during germination and early seedling growth by assaying annexin expression levels in dry and germinating seeds and in 7-day-old light-grown seedlings. Our results indicate that transcripts for all eight annexins are present in germinating seeds and that transcript levels for all the annexins increase by 7 days of normal growth. We assayed transcript levels in dark grown roots, cotyledons, and hypocotyls and found that the relative abundance of each annexin varied in these dark-grown tissues. We also examined the effects of red and far red light treatments on annexin expression in 5.5-day-old etiolated seedlings. Light treatments significantly altered transcript levels in hypocotyls and cotyledons for only two members of the gene family. Finally, we monitored annexin expression changes in response to a variety of abiotic stresses. We found that the expression of most of the Arabidopsis annexin genes is differentially regulated by exposure to salt, drought, and high- and low-temperature conditions, indicating a likely role for members of this gene family in stress responses.