A temperature induced lipocalin gene from Medicago falcata (MfTIL1) confers tolerance to cold and oxidative stress.

Abstract

Temperature-induced lipocalins (TIL) are plasmalemma-localized proteins and responsive to environmental stresses. Physiological functions of MfTIL1 from Medicago sativa subsp. falcata (L.) Arcang. (hereafter falcata), a forage legume with cold and drought tolerance, were investigated in this study. MfTIL1 expression was greatly induced by 4-96h of cold treatment, while transcript levels of the orthologs in Medicago truncatula, a model legume plant with lower cold tolerance than falcata, were reduced or not altered within 48-96h. MfTIL1 expression was not responsive to dehydration and salinity. Compared to the wild type, transgenic tobacco plants overexpressing MfTIL1 had lower temperature (LT50) that resulted in 50% lethal and elevated survival rate in response to freezing, elevated F v/F m and decreased ion leakage after treatments with chilling, high light and methyl viologen (MV). H2O2 and O2 (-) were less accumulated in transgenic plants than in the wild type after treatments with chilling, high light and MV, while antioxidant enzyme activities showed no difference between the two types of plants prior to or following treatments. Higher transcript levels of NtDREB3 and NtDREB4 genes were observed in transgenic plants than in the wild type under non-stressed conditions, but higher transcript levels of NtDREB1, NtDREB2, NtDREB4 and NtCOR15a genes under chilling conditions. It is suggested that MfTIL1 plays an important role in plant tolerance to cold and oxidative stress through promoted scavenging of reactive oxygen species and up-regulating expression of multiple cold responsive genes.