Effects Of Exogenous Spermine On Salt Iolerance And Gene Expression Of Proline Biosymthesis Pathway In Kosteletzkya Virginica

Proline accumulation is one of the most important adaptations to plant osmotic stress.Exogenous application of spermine could alleviate the salt injuries of Kosteletzkya virginica seedlings via increasing the proline accumulation under salt stress. With halophyte Kosteletzkya virginica as the material, we studyed the effect of the SPM on the seedlings of Kosteletzkya virginica under salt stress in dry weight, proline, malondialdehyde content and antioxidant enzyme activities, the results showed that exogenous SPM could increase the plant dry weight, the activities of CAT,SOD,POD enhance proline accumulation and reduce salt injury to seedlings K.virginica salt stress.Meanwhile, we researched the effect of the SPM on the two key enzymes of proline synthesis genes about the expression of P5CS and OAT. Results of relatively quantitative comparison revealed by realtime RT-PCR showed that although both transcripts of P5CS and OAT, the key genes involved in glutamate pathway and ornithine pathway of proline biosynthesis respectively, increased when K. virginica was exposed to NaCl stress, there was a differential response tendency for their expressions in roots and in leaves. OAT transcript was significantly upregulated in roots under stress, while P5CS transcript was more upregulated in leaves. Especially when K. virginica was exposed to 200mM NaCl stress, OAT transcript was more responsively augmented in roots with prolonged time course, however, P5CS transcript was more responsively regulated in leaves. The 60μM SPM dosage applied jointly with NaCl stress elevated OAT transcript significantly both in roots and leaves of K. virginica in comparison with NaCl stress alone. However, the effect of SNP on the upregulation of P5CS was apparently only in roots of K. virginica compared with NaCl stress alone. These results suggest that in K. virginica plantlets, both ornithine pathway and glutamate pathway play an important role in the proline accumulation during osmotic stress. And results also suggest that low dosage of SNP as NO donor can regulate both P5CS and OAT transcripts in the proline biosynthesis to enhance the salt tolerance of K. virginica.