oris . ▁ ▁P . ▁past oris ▁as ▁an ▁experimental ▁model ▁organ ism ▁As ▁an ▁experimental ▁model ▁organ ism , ▁P . ▁past oris ▁was ▁mainly ▁used ▁as ▁the ▁host ▁system ▁for ▁transformation . ▁Due ▁to ▁its ▁ab l ities ▁of ▁recom bin ation ▁with ▁foreign ▁DNA ▁and ▁processing ▁large ▁ ▁prote ins , ▁much ▁research ▁has ▁been ▁carry ▁out ▁to ▁investigate ▁the ▁possibility ▁of ▁producing ▁new ▁prote ins ▁and ▁the ▁function ▁of ▁artificial ly ▁designed ▁prote ins , ▁using ▁P . ▁past oris ▁as ▁a ▁transformation ▁host . ▁In ▁the ▁last ▁de cade , ▁P . ▁past oris ▁was ▁engine ered ▁to ▁build ▁expression ▁system ▁platforms , ▁which ▁is ▁a ▁typical ▁application ▁for ▁a ▁standard ▁experimental ▁model ▁organ ism , ▁as ▁described ▁below . ▁ ▁P . ▁past oris ▁as ▁expression ▁system ▁platform P . ▁past oris ▁is ▁frequently ▁used ▁as ▁an ▁expression ▁system ▁for ▁the ▁production ▁of ▁heter olog ous ▁prote ins . ▁Several ▁properties ▁make ▁P . ▁past oris ▁su ited ▁for ▁this ▁task . ▁Currently , ▁several ▁stra ins ▁of ▁ ▁P . ▁past oris ▁are ▁developed ▁for ▁different ▁requirements ▁of ▁the ▁expression ▁system . ▁Most ▁of ▁them ▁have ▁a ▁mut ation ▁in ▁the ▁H IS 4 ▁gene , ▁leading ▁to ▁the ▁selection ▁of ▁cells ▁which ▁are ▁transformed ▁successfully ▁with ▁expression ▁vectors . ▁The ▁technology ▁for ▁vector ▁integration ▁into ▁P . ▁past oris ▁gen ome ▁is ▁similar ▁to ▁that ▁in ▁Sac char omy ces ▁c ere vis iae . ▁ ▁Adv antage ▁ 1 : P . ▁past oris