Calmodulin7 Plays an Important Role as Transcriptional Regulator inArabidopsisSeedling Development

Abstract

Although calmodulin (CaM) is known to play multiple regulatory roles in eukaryotes, its direct function as transcriptional regulator is unknown. Furthermore, the physiological functions of CaM are largely unknown in plants. Here, we show that one of the four Arabidopsis thaliana CaM isoforms, CAM7, is a transcriptional regulator that directly interacts with the promoters of light-inducible genes and promotes photomorphogenesis. CAM7 overexpression causes hyperphotomorphogenic growth and an increase in the expression of light-inducible genes. Mutations in CAM7 produce no visible effects on photomorphogenic growth, indicating likely redundant gene functions. However, cam7 mutants display reduced expression of light-inducible genes, and cam7 hy5 double mutants show an enhancement of the hy5 phenotype. Moreover, overexpression of CAM7 can partly suppress the hy5 phenotype, indicating that the two factors work together to control lightinduced seedling development. The mutational and transgenic studies, together with physiological analyses, illustrate the concerted function of CAM7 and HY5 basic leucine zipper transcription factor in Arabidopsis seedling development.

Molecular Interactions of GBF1 with HY5 and HYH Proteins during Light-mediated Seedling Development in Arabidopsis thaliana

“…Furthermore, although hyh mutants do not display any morphological defects in WL (23), the hypocotyl length of gbf1 hyh double mutants indicates that hyh partially suppresses the phenotype of gbf1 mutants in WL. Such redundant functional relationships have also been observed with HY5 and CAM7 (14). Furthermore, BL-mediated induction of RBCS-1A was also found to be antagonistically regulated by GBF1 and HY5 or HYH.…”

“…So far, HY5 and CAM7/ZBF3 are two positive regulators known of light signaling pathways that act downstream of multiple photoreceptors, including phytochromes and cryptochromes (5,(12)(13)(14). HY5 has been genetically defined as a positive regulator of photomorphogenesis based on its partially etiolated phenotype in light-grown mutant seedlings (15)(16)(17)(18).…”

Functional Interconnection of MYC2 and SPA1 in the Photomorphogenic Seedling Development of Arabidopsis

“…The coimmunoprecipitated genomic DNA fragments with MYC2-cMyc were analyzed by real-time PCR. The amount of DNA fragment of the SPA1 promoter coimmunoprecipitated from the transgenic seedlings was found to be about 12-fold enriched as compared with the overexpresser cMyc-CAM7 transgenic seedlings (used as a control; Kushwaha et al, 2008;Fig. 1C).…”

“…Although the molecular and physiological functions of calmodulin (CaM) remain largely unknown in plants, various studies suggest that Ca 2+ /CaM is involved in light-mediated seedling development and gene expression. Detailed mutational, transgenic, and physiological studies have recently demonstrated that HY5 and CAM7 function in a synergistic or additive manner to promote photomorphogenic growth and lightregulated gene expression (Kushwaha et al, 2008).…”

A loss-of-function mutation in Calmodulin2 gene affects pollen germination in Arabidopsis thaliana

“…In Arabidopsis, only two members of this gene family have been functionally characterized, CAM3 (Zhang et al 2009) and CAM7 (Kushwaha et al 2008).…”