Research Of Physiology And Biochemistry In Saccharomy Cescerevisiae Transformed With Hsp70from Porphyra Haitanensis

The plasmids with hsp70gene from Porphyra haitanensis (denoted as phhsp70) had beenreconstructed in our group, which had been transformed into the wild type yeast strain BY4741and the ssa3hsp70knocked-out yeast strain YBL075c. The differences in growth, expression ofmRNA and oxidation resistance of four yeasts strains (BC: wild, B: overexpressed, Y:compensatory and YC: defective) under and after heat shock were investigated.The expressions of P. haitanensis hsp70gene in four yeasts strains under heat shock andat normal conditions were detected by appling the real-time quantitative PCR （RTQ-PCR）technique with the18s rDNA gene as the internal reference. The expressions of the gene weredetected in two yeast strains transformed with P. haitanensis hsp70gene (stain B and Y) while theother two (strain BC and YC) had no transgenic discovered. The results showed that the mRNAstranscribed from P. haitanensis hsp70gene increased after a short period of heat shock and variedrhythmically in the transformants (strain B and Y). The expression of P. haitanensis hsp70genein strain B and strain Y maintained stably at a low level as half of the control samples (strain BCand YC) when they were cultured in normal conditions after heat shock. The growthcharacteristics under sustainable heat shock were quite different within the transformates and thecontrols. The yeasts without P. haitanensis hsp70gene (BC and YC) hardly grew under heatshock while the transformed yeasts strain (B,Y) grew well closing to the situation in normalconditions.The expression of exogenous hsp70gene from P. haitanensis could help the yeastsobtained higher heat tolerance as well as to some extent facilitate cell growth at normaltemperature. It may improve the activity of antioxidant enzymes and remove more ReactiveOxygen Species (ROS) which makes the yeasts survive in heat shock or at normal temperature.At normal conditions, the transformed yeasts had higher antioxidant activities than the control, butthe difference is not siginificantely. It suggested that the antioxidation regulation system of theyeasts is mainly based on their endogenous systems while the expression of P. haitanensis hsp70 was just assistance. We may come to the conclusions that the transformation of P. haitanensishsp70could improve the heat resistance in yeasts, which may have some influences on ROSremoval.