OVEREXPRESSION OF PTRLEA7,A LATE EMBRYOGENESIS ABUNDANT FAMILY GENE FROM PONCIRUS TRIFOLIATA,CONFERS ENHANCED DROUGHT TOLERANCE BY ENHANCING ANTIOXIDANT CAPACITY

Late embryogenesis abundant(LEA)genes encode highly hydrophilic proteins that are essential in abiotic stress responses.However,most LEA genes in higher plants have not yet been investigated.This study identified an LEA family gene(PtrLEA7)from Poncirus trifoliata and studied its function in drought tolerance.The full-length coding sequence of PtrLEA7 was 420 bp encoding a protein of 139 amino acids.Phylogenetic analysis shows that PtrLEA7 protein belongs to the LEA_4 subfamily.Expression profiling by qPCR found that PtrLEA7 was strongly induced by dehydration,cold and ABA treatments,and slightly induced by salt stress.Subcellular localization reveals that PtrLEA7 protein was located in both cytoplasm and nucleus.To investigate its function,transgenic plants of both tobacco and Poncirus trifoliata overexpressing PtrLEA7 were obtained.Stress tolerance assays show that overexpression lines had enhanced dehydration and drought tolerance compared with wild type plants,indicating that PtrLEA7 positively regulates drought tolerance.In addition,transgenic plants had much higher expression levels of three antioxidant enzyme genes(CAT,SOD and POD)and significantly increased catalase enzyme activity,accompanied by reduced reactive oxygen species accumulation in comparison with wild type plants.Collectively,this study demonstrates that PtrLEA7 can confer enhanced drought tolerance partially via enhancing antioxidant capacity.

Identification and Characterization of a LEA-like Gene, CaMF5,Specifically Expressed in the Anthers of Male-fertile Capsicum annuum

To improve the understanding of molecular mechanisms of anther and/or pollen development in Chili pepper, in the present study, fulllength cDNA and DNA sequences of the pollen development-related gene CaMF5 were obtained from the anthers of a Capsicum annuum nuclear male-fertile line. Sequence analysis indicated that the full length of CaMF5 was 747 bp, containing a maximum opening reading frame of 447 bp.Amino acid sequence alignment and phylogenetic analysis revealed that CaMF5 shared approximately 37%–77% homology with a series of uncharacterized or hypothetical proteins and late embryogenesis abundant(LEA) proteins from other plants. However, no LEA structural domain was detected in CaMF5, which indicated that it might be a new type of LEA gene. CaMF5 was only expressed in flower buds at stages 7 and 8 and in open flowers of the male-fertile line, whereas it exhibited no expression in any examined organs of the male-sterile line. In addition, CaMF5 showed the highest transcript abundance in the anthers of the male-fertile line, with no expression being detected in any other examined organs, such as the sepals, petals, pistils, roots, stems, or leaves. Taken together, our results suggest that CaMF5 is an anther-specific gene that might encode a new type of LEA protein related to anther and/or pollen development in C. annuum.

Two New Group 3 LEA Genes of Wheat and Their Functional Analysis in Yeast

The group 3 late embryogenesis abundant （LEA） proteins are thought to protect cells from stresses associated with dehydration during periods of water deficit. To investigate the functions of different members of the group 3 LEA genes, we isolated and characterized two new group 3 LEA genes, namely TaLEA2 and TaLEA3, from wheat （Triticum aestivum L.） and introduced TaLEA2 and TaLEA3 into Saccharmyces cerevisiae to examine the effect of these genes on yeast cell tolerance to osmotic, salt, and cold stresses. The TaLEA2 gene encoded a protein of 211 amino acids and possessed five repeats of 11-mer amino acid motifs. The TaLEA3 gene encoded a polypeptide of 211 amino acids with nine repeated units. Overexpression of TaLEA2 and TaLEA3 improved stress tolerance in transgenic yeast cells when cultured in medium containing sorbitol, salt and-20℃ freezing treatments respectively. However, the yeast transformants with TaLEA2 seemed to be more tolerant to hyperosmotic and freezing stress than transformants with TaLEA3. This implies that a close relationship exists between function and the number of repeats of the 11- mer amino acid motif in the group 3 LEA protein.