Arabidopsis TCH3 Encodes a Novel Ca 2+ Binding Protein and Shows Environmentally Induced and Tissue-Specific Regulation

Abstract

The Arabidopsis touch (TCH) genes are up-regulated in response to various environmental stimuli, including touch, wind, and darkness. Previously, it was determined that TCH1 encodes a calmodulin; TCH2 and TCH3 encode calmodulin-related proteins. Here, we present the sequence and genomic organization of TCH3. TCH3 is composed of three repeats; remarkably, the first two repeats share 94% sequence identity, including introns that are 99% identical. The conceptual TCH3 product is 58 to 60% identical to known Arabidopsis calmodulins; however, unlike calmodulin, which has four Ca2+ binding sites, TCH3 has six potential Ca2+ binding domains. TCH3 is capable of binding Ca2+, as demonstrated by a Ca(2+)-specific shift in electrophoretic mobility. 5' Fragments of the TCH3 locus, when fused to the beta-glucuronidase (GUS) reporter gene, are sufficient to confer inducibility of expression following stimulation of plants with touch or darkness. These TCH3 sequences also direct expression to growing regions of roots, vascular tissue, root/shoot junctions, trichomes, branch points of the shoot, and regions of siliques and flowers. The pattern of expression of the TCH3/GUS reporter genes most likely reflects expression of the native TCH3 gene, because immunostaining of the TCH3 protein shows similar localization. The tissue-specific expression of TCH3 suggests that expression may be regulated not only by externally applied mechanical stimuli but also by mechanical stresses generated during development. Consequently, TCH3 may perform a Ca(2+)-modulated function involved in generating changes in cells and/or tissues that result in greater strength or flexibility.

Characterization and Immunolocalization of a Cytosolic Calcium-Binding Protein from Brassica napus and Arabidopsis Pollen1

“…For mobility-shift assays, the conditions were as described previously (Sistrunk et al, 1994). Protein was mixed with 10 mm EGTA, 10 mm CaCl 2 plus 2 mm EGTA, or 10 mm MgCl 2 plus 2 mm EGTA prior to electrophoresis on native-PAGE gels (Ausubel et al, 1988).…”

Two Seven-Transmembrane Domain MILDEW RESISTANCE LOCUS O Proteins Cofunction inArabidopsisRoot Thigmomorphogenesis

“…Indeed, rapid and transient changes in the concentration of cytosolic free Ca 2+ levels (Ca 2+ spikes) were observed upon mechanical stimulation in roots (Knight et al, 1991;Legué et al, 1997). Cloning of a set of touchinduced genes, of which three encode either calmodulin or calmodulin-related proteins, and identification of a plasma membrane protein that links mechanosensing with Ca 2+ influx provides genetic evidence for the importance of Ca 2+ signaling in this physiological process (Braam and Davis, 1990;Sistrunk et al, 1994;Nakagawa et al, 2007a).…”

Multiple calmodulin-like proteins in Arabidopsis are induced by insect-derived (Spodoptera littoralis) oral secretion

“…It is rapidly induced by mechanical stimulation, ethylene, auxin, cold, and extracellular calcium. [14][15][16][17][18] Plants respond to two concomitant stimuli of herbivory: mechanical wounding and recognition of elicitors in OS. The sustained expression of CML12 could be due to the fact that it is also upregulated by mechanical wounding alone and OS might act to amplify the wound-induced signal.…”