Plants confront with different environmental and abiotic stress stimuli such as cold,drought and salinity, which affect growth and development and limits plant productivityand yield.Plants physiological and biochemical pathways respond to overcome stresschallenges.Calcium (Ca2+) has emerged as a significantsecondary messenger thatregulates the activities of hormonal and environmentalsignals that are associated withbiotic and abiotic stresses.Ca2+ binding proteins typically contain a Ca2+ binding EF-hand(a helix-loop-helix structure) motif.Calmodulin-like (CML) proteins are an importantCa2+ sensor and play a significant role in the mediating plant stress responsive mechanism.　　In this study, tomato genes encoding calmodulin-like (CML) proteins that possessEF-hand motifs, and no other identifiable functional domains were analyzed.Usinggenome analysis and BLAST searches in the database, 52 CML genes were identified intomato.Comprehensive analyzes, including evolutionary relationships, gene structures,chromosomal locations, functional annotations, and gene duplications, were performed.Distributionmapping exhibited that 52 SlCML genes containing different intror/exonpatternswere unevenly distributed among ten chromosomes.In addition, 24 SlCMLproteins were predicted as segmentally duplicated.Conserved motifs, promoter cisregulatory elements, organ-based expression patterns and expression analyzes indicatedthe potential responsiveness of SlCML proteins to abiotic stresses and phytohormones.These results illustrate the complexity of the CML gene family and indicate a potentiallyvital role for these molecules in tomato growth and development as Ca2+ signaltransducers.　　Furthermore, cold responsive calmodulin-like (ShCML44) gene was isolated fromcold tolerant wild tomato (Solanum habrochaites), and functionally characterized.TheShCML44 was differentially expressed in all plant tissues including root, stem, leaf,flower and fruit, and was strongly up-regulated under cold, drought and salinity stressesalong with plant growth hormones.Under cold stress,progressive increase in theexpression of ShCML44 was observed particularly in cold-tolerant S.habrochaites.The　　ShCML44-overexpressed plants showed greater tolerance to cold, drought, and salinitystresses, and improved germination and better seedling growth.Transgenictomato plantsdemonstrated higher antioxidant enzymes activity, gas exchange and water retentioncapacity with lower malondialdehyde accumulation and membranedamage under coldand drought stresses compared to wild-type.Moreover, transgenic plants exhibitedreduced reactive oxygen species and higher relative water contents under cold anddrought stress, respectively.Greater stress tolerance oftransgenic plants was furtherreflected by the up-/down-regulation of stress-related genes including SOD, GST, CAT,　　POD, LOX, PR and ERD.In crux, these results strengthen the molecular understanding ofShCML44 gene to improve the abiotic stress tolerance in tomato.　　Keywords: Abiotic stress; Calmodulin-like proteins (CML); Calmodulin; Solanum;Tomato; Expression pattern; Plant hormones; Cold tolerance; CML44。