ABSTRACT
To study the genetic basis of heat tolerance at anthesis, a set of chromosome segment substitution lines (CSSLs) derived from Sasanishiki (japonica ssp. heat susceptible) and Habataki (indica spp. heat tolerant) were used for analysis across three high temperature environments. Spikelet fertility (SF), daily flowering time (DFT) and pollen shedding level (PSL) under high temperature (HT) were assessed. Eleven related QTLs were detected, of which, two QTLs qSF (ht) 2 and qSF (ht) 4.2 for spikelet fertility were identified on chromosomes 2 and 4. Four QTLs qDFT3, qDFT8, qDFT10.1 and qDFT11 for daily flowering time were detected on chromosomes 3, 8, 10 and 11. The other five QTLs qPSL (ht) 1, qPSL (ht) 4.1, qPSL (ht) 5, qPSL (ht) 7 and qPSL (ht) 10.2 on chromosomes 1, 4, 5, 7 and 10, respectively, were found had effects both on spikelet fertility and pollen shedding level. Of the 11 QTLs, 8 were overlapped with QTLs reported by others, 3 QTLs qPSL (ht) 4.1, qPSL (ht) 7 and qPSL (ht) 10.2 identified in this study were novel. The stability of qPSL (ht) 4.1 was further verified at different temperatures, which could be used to improve the pollen shedding and pollen growth on stigma for rice heat-tolerance breeding.
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 4-96 h 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 48-96 h. 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.
Subject(s)
Acclimatization , Gene Expression Regulation, Plant , Lipocalins/genetics , Medicago/physiology , Nicotiana/physiology , Amino Acid Sequence , Antioxidants/metabolism , Cold Temperature , DNA, Complementary/genetics , Gene Expression , Genes, Reporter , Hydrogen Peroxide/metabolism , Lipocalins/metabolism , Medicago/genetics , Molecular Sequence Data , Onions/cytology , Onions/genetics , Onions/metabolism , Oxidative Stress , Plant Leaves/genetics , Plant Leaves/physiology , Plant Proteins/genetics , Plant Proteins/metabolism , Plants, Genetically Modified , Reactive Oxygen Species/metabolism , Sequence Alignment , Nicotiana/geneticsABSTRACT
A full length cDNA encoding a myo-inositol transporter-like protein, named as MfINT-like, was cloned from Medicago sativa subsp. falcata (herein falcata), a species with greater cold tolerance than alfalfa (M. sativa subsp. sativa). MfINT-like is located on plasma membranes. MfINT-like transcript was induced 2-4 h after exogenous myo-inositol treatment, 24-96 h with cold, and 96 h by salinity. Given that myo-inositol accumulates higher in falcata after 24 h of cold treatment, myo-inositol is proposed to be involved in cold-induced expression of MfINT-like. Higher levels of myo-inositol was observed in leaves of transgenic tobacco plants overexpressing MfINT-like than the wild-type but not in the roots of plants grown on myo-inositol containing medium, suggesting that transgenic plants had higher myo-inositol transport activity than the wild-type. Transgenic plants survived better to freezing temperature, and had lower ion leakage and higher maximal photochemical efficiency of photosystem II (Fv /Fm ) after chilling treatment. In addition, greater plant fresh weight was observed in transgenic plants as compared with the wild-type when plants were grown under drought or salinity stress. The results suggest that MfINT-like mediated transport of myo-inositol is associated with plant tolerance to abiotic stresses.