Molecular characterization of a calmodulin gene, VcCaM1, that is differentially expressed under aluminum stress in highbush blueberry

Authors: INOSTROZABLANCHETEAU, CLAUDIO - Universidad De La Frontera; AQUEA, FELIPE - University Of Catolica De Chile; LOYOLA, RODRIGO - University Of Catolica De Chile; Slovin, Janet

Submitted to: Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2012
Publication Date: 4/29/2013
Citation: Inostrozablancheteau, C., Aquea, F., Loyola, R., Slovin, J.P. 2013. Molecular characterization of a calmodulin gene, VcCaM1, that is differentially expressed under aluminum stress in highbush blueberry. Plant Biology. 15:1013-1018.

Interpretive Summary: Blueberry is often grown in acidic and poorly drained soils that render plants susceptible to aluminum toxicity. Aluminum toxicity results in poor plant growth, and in extreme cases, plant death. Two varieties of blueberry, one resistant and one sensitive to aluminum, had previously been analyzed to find out which genes were activated when plants were grown on soils that cause aluminum toxicity. One of the genes that were activated in aluminum resistant but not in aluminum sensitive blueberry plants is called calmodulin. We cloned this gene and characterized its activity. Although this gene is activated in resistant plants, our results indicate that calmodulin is not directly responsible for the observed resistance to aluminum toxicity. These results are of use to small fruit researchers who are trying to understand plant mechanisms for tolerating aluminum in soils so that they can produce more aluminum tolerant plants.

Technical Abstract: Calmodulin (CaM), a small acidic protein, is one of the best characterized Ca2+ sensors in eukaryotes. This Ca2+-regulated protein plays a critical role in decoding and transducing environmental stress signals by activating specific targets. Many environmental stresses elicit changes in intracellular Ca2+ activity that could initiate adaptive responses under adverse conditions. We report the first molecular cloning and characterization of a calmodulin gene, VcCaM1 (Vaccinium corymbosum Calmodulin 1), in the woody shrub, highbush blueberry. VcCaM1 was first identified as VCAL19, a gene induced by aluminum stress in V. corymbosum L. A full-length cDNA of VcCaM1 containing a 790-bp open reading frame (ORF) encoding 149 amino acids was cloned from root RNA. The sequence encodes four Ca2+-binding domains (EF-hands) and shows high similarity (99%) with the isoform CaM 201 of Daucus carota. Expression analyses showed that following Al treatment, VcCaM1 message level decreased in roots of Brigitta, an aluminum resistant cultivar, and after 48 hr, were lower than that found in Bluegold, an aluminum sensitive cultivar. VcCAM1 message decreased also in leaves of both varieties within two hr of treatment. Message levels in leaves then increased by 24 hr to control levels in Brigitta, but not in Bluegold, but then decreased again by 48 hr. In conclusion, VcCaM1 does not appear to be directly involved in Al resistance, but may be involved in improved plant performance under Al-toxicity conditions through regulation of Ca2+ homeostasis and antioxidant systems in leaves.