The Difference Of Rubisco In Two Ecotypes Of Reeds From Different Habitats

Reed(Phragmites communis Trin.)is a kind of herbage plant living for several years. The representative environment is freshwater or salt lake and marshland. As the adaption to the different environments, they can evolve to different ecotypes possessing more resistance/tolerance and stable genetic differences.According to their habitats and characteristics,growing in Hexi corridor are divided into four different ecotypes,refered to as swamp reed(SR),dune reed(DR),light salt meadow reed(LSMR) and heavy salt meadow reed(HSMR). Studies have been conducted on plant physiology, biochemistry and molecular biology in different ecotypes reeds for a long period in our laboratory.In this work, Rubisco in two ecotypes of reed leaves,DR and SR,were investigated for the contents of Rubisco and its SH, the hydrophobicity and hydrophilicity of its peptides, degradated by trypsin, peptide mass fingerprinting,and so on.With the optimization of Rubisco's separation and purification ,we found that the content of Rubisco in DR leaves were lower than those of SR,and the extraction percentage of Rubisco in DR were remarkably lower than tose of SR.These results suggest that PAAC can bond Rubisco and help to its stabilization in drought stress environment.In addition, PAAC was the specific compound in DR, nonexistence in SR.The result showed that there was no modification in molecular weight of Rubisco large and small subunit to DR.For both DR and SR,the molecular weight of Rubisco large subunit are about 56kD,and the molecular weight of Rubisco small subunit are about 15.5kD.In drought stress environment.the Rubisco'SH content of DR was remarkably lower than those of SR.This result can help to reduce the probability of S-S formation,so the probabilities of protein agglutination and denaturation are also reduced. Rubisco's peptides, degradated by trypsin were separated by RT—HPLC, and we found that compared with the SR,the proportion of hydrophilic Aa was increased in DR.This result suggest that the Aa composition of Rubisco of reed has changed by drought stress.We analyse the enzymloysis peptides of DR and SR by MALDI-TOF-MS,There were 25 peptides of DR and 24 peptides of SR checked out.During these peptides.there were 14 peptides anastomosed in molecular weight,which demonstrate these peptides' Aa sequences were same.To those different peptides of molecular weight,we presumed that it's the result of the variation in structure of Rubisco.With all these results,we hold that compared with SR,the primary structure and higher structure of DR Rubisco are different.The Rubisco of DR have adapted to the drought stress environment in gene expression,and there were differences in genotype between DR and SR.The result discussed above also confirmed that in a long time to adapt to the environment,some conservative proteins of plant,such as Ruisco,would chang in its molecular to the adaptive need.