SCREENING OF CELL WALL-DEFECTIVE MUTANTS AND CONSTRUCTION OF TRANSFORMATION SYSTEM IN CHLORELLA VULGARIS

Chlorella vulgaris has been widely recognized as a safe food ingredient due to its richness in proteins, vita-mins, minerals and short chain poly-unsaturated fatty acid. Recently, Chlorella vulgaris was chosen as one of the feedstock for biodiesel because of its high growth rate and high lipid content, but lacking of stable and efficient transformation system has seriously hindered the understanding of lipid metabolism and the development of the genetic engineering. Our aim was to obtain cell wall-defective mutants of Chlorella vulgaris and use them to construct an electro-transformation system. Based on the release ability of chlorophyll after treatment of 1% Triton X-100, we set up a high throughput screening method of cell wall-defective mutants and obtained 10 cell wall-defective mutants. In addition, we constructed a transformation vector pHK203 by using endogenous promoter and 3'-UTR of -tubulin gene and by using AphⅧ as selective marker. We successfully obtained 40 transformants per g DNA using plasmid pHK203 and ddH2O as electroporation buffer with the best electroporation condition of 1500 V, 525 , 50 F. Our study will benefit the study of lipid metabolism pathway and genetic engineering of Chlorella vulgaris.