Abstract
In plants, the calmodulin (CaM) proteins is an important calcium-binding protein, which play a crucial role in both regulating plant growth and development, as well as in the resistance mechanisms to various biotic and abiotic stresses. However, there is limited knowledge available on the CaM family functions in Solanum pennellii, a wild tomato species utilized as a genetic resource for cultivated tomatoes. In this study, 6 CaM (SpCaM) and 45 CaM-like (SpCML) genes from Solanum pennellii were selected for bioinformatics analysis to obtain insights into their phylogenetic relationships, gene structures, conserved motifs, chromosomal locations, and promoters. The results showed that the 6 SpCaM proteins contained 4 EF-hand domains each, and the 45 SpCML proteins had 2-4 EF-hand domains. The 51 CaM and CaM-like genes contained different intron/exon patterns and they were unevenly distributed across the 12 chromosomes of S. pennellii. The results of the analysis of the conserved motifs and promoter cis-regulatory elements also indicated that these proteins were involved in the responses to biotic and abiotic stresses. qRT-PCR analysis indicated that the SpCaM and SpCML genes had broad expression patterns in abiotic stress conditions and with hormone treatments, in different tissues. The findings of this study will be important for further investigations of the calcium signal transduction mechanisms under stress conditions and lay a theoretical foundation for further exploration of the molecular mechanisms of plant resistance.
Highlights
Plants are invariably subjected to stressful environmental conditions and pathogenic attacks from various bacteria, fungi, and viruses throughout their lives
The results revealed that cis-acting elements associated with responses to phytohormones, such as abscisic acid (ABRE), salicylic acid (TCA-element and W-box), gibberellin (GARE-motif), methyl jasmonate (CGTCA-motif), ethylene (ERE) and auxin (TGA-element); adversity, such as anoxia stress (ARE), low temperature (LTR), light (Sp1 and I-box), drought (MBS), dehydration (DRE); and defense and stress-related elements (TC-rich repeats) occurred widely in the promoter regions of the SpCaM, and SpCML. 78.4% of the 51 genes contained ARE, while 72.5% contained ABRE, and 70.6% contained CGTCA-motif and ERE
Heat shock proteins (HSPs) induced by high temperatures are regulated by heat shock transcription factors (HSFs)
Summary
Plants are invariably subjected to stressful environmental conditions and pathogenic attacks from various bacteria, fungi, and viruses throughout their lives. Each of the 4 EF-hand domains binds to a Ca2+, and this binding changes the conformation of the CaM, thereby activating it to perform signal transductions. Another class of proteins, called CML, are structurally similar to the CaM and contain 1 to 4 EF-hand domains. AtCML23 and AtCML24 proteins reduce the level of NO by transmitting calcium signals, which result in inhibition of the FLOWERING LOCUS C (FLC) gene expression, affecting the autonomic regulatory pathway of the transition to flowering[28]. MAPK (mitogen-activated protein kinase) phosphatase (MKPs) are negative regulators of MAPKs. The wheat MKP (TMKP) contains a CaM binding domain and binds to CaM in a Ca(2+)-dependent manner[30]. The overexpression of Arabidopsis CML8, improved resistance to pathogenic bacteria[32]
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