Functional analyses of lipocalin proteins in tomato

In this study, two temperature-induced lipocalin genes SlTIL1 and SlTIL2, and a chloroplastic lipocalin gene SlCHL were isolated from 'Micro-Tom' tomato. The coding sequences of SlTIL1, SlTIL2 and SlCHL were 558, 558, and 1002 bp, respectively. By TargetP analysis, no characteristic transit peptides were predicted in the proteins of SlTIL1 and SlTIL2, while a chloroplastic transit peptide was predicted in the protein of SlCHL. The subcellular localization results indicated that SlTIL1 and SlTIL2 proteins were major localized in the plasma membrane, while SlCHL was localized in chloroplast. To understand the function of lipocalins, transgenic tomato over-expressed SlTIL1, SlTIL2 and SlCHL and their virus-induced gene silencing (VIGS) plants were generated. The phenotypes were significantly affected when the SlTIL1, SlTIL2 and SlCHL were over-expressed or silenced by VIGS, which suggested that the three lipocalins played important roles in regulating the growth and development of tomato. In addition, the level of ROS (O₂ ^- and H₂O₂) was low in SlTIL1, SlTIL2 and SlCHL over-expressed plants, while it was high in their silenced plants. The changes in the expression of SODs were consistent with the accumulations of ROS, which indicated that lipocalins might have an important role in abiotic oxidative stress tolerance in tomato plants. Especially SlTIL1 and SlTIL2 are localized around their membranes and protect them from ROS. The results will contribute to elucidating the functions of lipocalin in plants, and provide new strategies to improve the tolerance to abiotic stress in tomato plants.