Development of Transgenic Potato with Increased Starch Production

Potato (Solanum tuberosum) is one of the major crop and staple food with around 5000 varieties worldwide. Despite many folds increase in yield of potato, it has not yet been used fully for starch production on commercial scale because of non-availability of improved potato varieties with high starch content. The present paper reports production of transgenic potatoes of commercial potato cultivars, Kufri Sudej and Kufri Pukhraj with high starch content. This was achieved by expressing mutated as well as wild type glgC genes (encoding AGPase, the key enzyme in starch biosynthesis) cloned from the genomic DNA of E.coli K12 strain. AGPase catalyses the rate limiting step in starch biosynthesis and therefore the expression of more active bacterial form of the enzyme was expected to increase starch production. This was achieved by modifying E. colt glgC gene by site directed mutagenesis to G336D in order to abolish allosteric regulation by fructose-1,6 bisphosphate (FBP). The transgenicity was checked by PCR amplification of nptil selectable marker as well as glgC gene. An analysis of the starch content of 12 transgenic lines of Kufri Sutlej and 28 lines of Kufri Pukhraj revealed that most of the transgenic lines harboring mutated glgC gene showed increased starch content. However, no significant increase in starch content was observed in transgenic lines with wild type glgC gene. Among 40 transgenic lines, mutated transgenic lines KSglgCM2 of Kufri Sudej and KPglgCM2 of Kufri Pukhraj showed 83.32% and 37.32% increase in starch content, respectively and emerged as potential candidate which can be used in processing sector on commercial scale.