Genome-wide identification of SlIQMs and the regulatory effect of calcium on tomato seedlings under drought stress and phytohormone treatment.

SlIQMs were identified, exogenous calcium and phytohormones induced their expression. SlIQMs's function were verified by VIGS. Calcium synergistically promoted seedling growth with ABA, IAA, MeJA and antagonized growth inhibition with GA or SA. The IQM genes, are crucial members of the calmodulin-binding protein family, play pivotal roles in plant growth and stress response. However, the existence and impact of IQM in tomato remain unclear. This study demonstrates that the SlIQMs are randomly distributed across the 4 chromosomes of tomato and exclusively located within the nucleus. Phylogenetic analysis classifies the SlIQMs into 3 distinct subclasses. Analysis of cis-acting elements reveals that SlIQMs may function in stress or hormone process. Quantitative reverse-transcriptase PCR analysis further testified that polyethylene glycol (PEG), abscisic acid (ABA), indole acetic acid (IAA), gibberellin (GA), methyl jasmonate (MeJA), and salicylic acid (SA) induce expression levels of SlIQM1/2/3/5/6/7. Furthermore, exogenous calcium significantly alleviates detrimental effects on seedlings growth leaded by drought stress. Moreover, the relationships between hormones and calcium were explored. The results showed that calcium synergistically promoted the seedlings growth with ABA, IAA and MeJA, however antagonistic effects on inhibiting growth are observed between calcium and GA or SA. The virus-induced silencing of 6 candidate genes caused growth inhibition of tomato seedlings under drought stress and phytohormone treatment. These findings lay the foundation for a comprehensive study of the structure and biological function of SlIQM genes and the interaction between calcium and different plant hormones on plant growth.