Calmodulin-binding transcription activator 1 mediates auxin signaling and responds to stresses in Arabidopsis

Abstract

Auxin is a key plant hormone that regulates various aspects of plant development. However, the mechanisms integrating auxin growth effects with stress responses are not fully understood. In this study, we investigated the possible role of calmodulin-binding transcription activator 1 (CAMTA1), an Arabidopsis thaliana calcium/calmodulin-binding transcription activator, in auxin signaling and its responses to different stresses. Plants harboring the AtCAMTA1 promoter fused to the GUS reporter gene revealed cell-specific expression patterns reminiscent of auxin responses. The responsiveness of CAMTA1 to auxin was further assessed by chemical disturbances in polar auxin transport, and by RT-PCR analysis of gene expression of dissected leaf sections from plants exposed to the auxin transport inhibitor NPA. Furthermore, the intensity and cell-specific expression patterns of CAMTA1 changed significantly and differentially on exposure to increasing salt concentrations and heat. Transcriptome analysis of a camta1 T-DNA insertion mutant revealed 63 up-regulated genes, of which 17 are associated with auxin signaling. Finally, analysis of hypocotyl elongation in the presence and absence of auxin revealed that camta1 T-DNA insertion mutants and CAMTA1-repressor lines are hyper-responsive to auxin compared to wild-type seedlings. Thus, CAMTA1 participates in auxin signaling and responds to abiotic stresses.

Global translational reprogramming is a fundamental layer of immune regulation in plants

“…efr-1 6 , ers1-10 (a weak gain-of-function mutant; ERS, ethylene receptor-related gene family member) 26 , ein4-1 (a gain-of-function mutant; EIN4, ethylene receptor-related gene family member) 27 , wei7-4 (a loss-of-function mutant; WEI7, involved in ethylene-mediated auxin increase) 28 , eicbp.b ( camta 1–3 ; SALK_108806; EICBP.B, an ethylene-induced calmodulin-binding protein) 29 , pab2/4 18 and pab2/8 18 were previously described. efr7 (SALK_205018; ERF7, a homologue of the ethylene responsive TF gene ERF1 ) and gcn2 (GABI_862B02) were from the Arabidopsis Biological Resource Center (ABRC).…”

Coping with Stresses: Roles of Calcium- and Calcium/Calmodulin-Regulated Gene Expression

“…The patterns of induction to multiple chemical and physical stimuli suggest the involvement of individual CAMTAs in multiple signal transduction pathways and stress responses. For example, CAMTAs have been shown to be involved in auxin signaling in growth and development as well as in stress response and may link the two pathways (Galon et al, 2010b). CAMTA1 repressor lines and camta1 mutants showed enhanced responsiveness to auxin, suggesting that in wild-type plants, enhanced expression of CAMTA1 in response to stresses suppresses the plant's responsiveness to auxin (Galon et al, 2010b).…”

Recent Advances in Calcium/Calmodulin-Mediated Signaling with an Emphasis on Plant-Microbe Interactions

“…Very recently, results showed that CAMTA1 and CAMTA2 share some functional redundancy with CAMTA3 in suppressing SA biosynthesis and the quick induction of CBF1, CBF2, and CBF3 transcription (Kim et al, 2013). AtCAMTA1 was reported to be an auxin-responsive gene, and hypocotyl elongation of AtCAMTA1 knockout or repression lines is hyperresponsive to exogenous application of auxin, indicating that CAMTA1 could regulate plant growth through the action of auxin (Galon et al, 2010a).…”