| Defensins is one kind of small, cysteine-rich short peptide from lower organisms to human beings. Its function has always been known as anti-pathogen, especially anti-fungus. It has a broad spectrum of antimicrobial activity even in low concentration, and is an important part of plant natural defense system. Recent reports proved that defensins also could be induced by abiotic stresses.Dehydrins are one kind of late embryogenesis abundant proteins, and were found in many kinds of plants. They could be induced by cold, drought and many other abiotic stresses. Some of them have already been used in agricultural production through the transgenic method.The fragments of a defensin encoding gene CiDe/2, and a dehydrin encoding gene CiDHN3 were found from the suppression subtractive hybridization (SSH) library of drought-treated Caragana intermedia seedlings constructed by our laboratory. RACE was taken to get the full-length sequences and confirmed. The open reading frame (ORF) of CiDe/2 is 225bp, and its gDNA is 372bp in length, it contains two exons and one intron. The ORF of CiDHN3 is 891bp and has no intron.The results of quantitative real-time PCR showed, CiDef2 responded to various abiotic stresses and hormones treatments, such as drought, NaCl, heat, cold, NAA, and ABA, its transcript increased over 100 times under drought and cold stress compared to that of the control. CiDHN3 can be induced by drought, NaCl and cold, and its transcription elevated over 40 times under drought treatment.The overexpression vector of these two genes were constructed and driven by CaMV 35S promoter, and were transformed into the wide-type Arabidopsis thaliana (Col-0). Homozygous transgenic lines were obtained by screening. Only CiDe/2 overexpression lines were found to show a higher germination rate than the wild-type, indicating that this gene could enhance tolerance of the transgenic seeds to salt stress during germination stage. |
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