Cloning And Analysis Of Salt-tolerance Function Of A BZIP Gene From Tamarix Androssowii

We cloned two bZIP sequences from the Tamarix plant cDNA library,TabZIP1 and TabZIP2.Full-length cDNA sequence of TabZIP1 is cloned by using 5'RACE method. Sequence analysis showed that the TabZIP1 gene is 1609 bp in length,including 1419 bp of open reading frame(ORF),and encodes a protein of 472 amino acids with a predicted molecular mass of 43.0kD and pI 9.47.Another full-length cDNA sequences obtained from Tmarix cDNA library is TabZIP2,TabZIP2 gene is 760 bp in length,including 435 bp of open reading frame(ORF),and encodes a protein of 144 amino acids with a predicted molecular mass of 16.5 kD and pI 6.60.Expression of TabZIP1 in Tamarix in response to abiotic stress was studied by real time RT-PCR.The results showed that the expression of TabZIP1 was induced by NaCl,and reached to the highest level after NaCl stress for 24 h,with 8.6 fold of expression level of control; however,the expression of TabZIP1 was inhibited by NaHCO₃ stress.The TabZIP2 gene was insert into the plant expressive vector of pROKâ…¡,the construct plant expression vector named pBZIP2.The TabZIP2 gene was transformed into tobacco by using Agrobacterium mediated transformation.The transgenic lines were examined by PCR and Southern hybridization,confirming that TabZIP2 gene have been integrated into the genome of tobacco.Northern hybridization approved that the foreign TabZIP2 gene was successfully expressed in all the transgenic lines.Four transgenic lines were used for the test of NaCl tolerance.Activity of POD,SOD, contents of MDA,relative conductance,content of soluble sugar,content of soluble proteins, relative growth rate and relative water cintent were measured and analysised under NaCl stress. The results showed that during NaCl stress 4d,the activity of POD,SOD,content of soluble proteins all reach the highest level,and have higher than that of the control.The MDA content and the relative conductivity were dropped for NaCl stress 4d,and increased at NaCl stress for 7 d.They were significantly lower than control plants during NaCl stress.Content of soluble sugar in some transgenic lines(B13,B18) has reached maximum levels,and obvisly higher than that of the control.The relative growth of transgenic in all transgenic lines were higher than that of control under NaCl stress.The result indicated that the TabZIP2 gene may mediate salt tolerance in plant through increasing of the ability of elimination of active oxygen,increasing of the content of soluble suguar,and regulation of soluble protein synthesis.