Though microscopic viruses can be harmful to plants and animals, they can also be an invaluable vector to infect plants after inserting foreign genes that produce exogenous proteins.
病毒，這種病原微生物，雖然會對動植物造成危害，但卻又是個不可多得的「載體」，可利用它殖入外來基因後再去感染植物，生產外源蛋白。