| Tamarix.spp has a high ability of resistance to salt, drought and freezing environment .Inthis study, a cap gene cloned from Tamarix.spp was inserted into yeast expression vector(pYES2) and plant expression vector (pROKⅡ), and transferred into yeast cells and Populusdavidiana X P. bolleana L. for functional analysis. The main results obtained were as thefollowings:(1) The recombinant plasmid pYES2-cap was constructed by inserting cap gene into yeastexpression vector pYES2, pYES2-cap was transferred into yeast NVSc1, and confirmed byPCR detection of 10 randomly picked INVSc1(pYES2-cap) lines.The expression of foreigncap gene in yeast was investigated by inducing INVSc1(harboring cap gene) strain and1NVSc1 (transformed with empty pYES2 vector) strain. Northern blotting showed that the capgene had been expressed successfully in yeast cells.(2) The yeast cells transformed with cap gene and control (transformed with emptypYES2 vector) were treated with some abiotic stress, including NaCl , Na2CO3, NaHCO3,drought, UV-rays.The results revealed that the survival rate of yeast cells transformed with capsignificantly higher than that of control under above stress treatments, indicating that theexpression of foreign cap gene had protected the yeast cells from damage under stresscondition, and the Tamarix cap gene can confer the ststress-resistance.(3) Several Kan resistant lines of Populus davidianaXP. bolleana L. were generated, and 8transgenic lines were picked and detected by PCR assay and Souther dot blotting. The resultsshowed that the cap gene had been integrated into the genome of these transgenic lines. TheRT-PCR and Northern Blotting detection were further confirmed that the cap gene had beenexpressed in transgenic plants.(4) The 7 transgenic lies and control (nontransgenic plants) were treated with cold stress,and the chlorophyll contents, relative electric conductivity and MDA contents were comparedbetween them. The results showed that the chlorophyll contents in control plants weredecreased Continually under cold stress, and the chlorophyll contents in transgenic lines were20.49％and 24％higher than that in control. The relative electric conductivity in transgeniclines was 33.88％lower than that in control plants. The MDA contents of transgenic andcontrol lines were 18.86～33.14μmol.g·-1 and 34.18μmol·g-1, respectively. These resultsdemonstrated that the cap gene confered the cold stress tolerance to transgenic Populusdavidiana X P. bolleana L.(5) Contents of malondialdehyde (MDA), relative electric conductivity in the 8transgenic lines were determined and analyzed under NaCl stress. When the transgenic lines were treated with 1.2 M NaCl, the average relative electric conductivity and MDA contentswere 15.34％and 23.21％lower than that in control, respectively. The above results indicatedthat the transgenic lines suffered minor damage under NaCl stress than control do.All the above results indicated that the constitutively expressed cap gene from T.androssowii can improve the ability of stress-resistance in transgenic plant, and the cap genecould confer cold and salt tolerance into transgenic plants.
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