Senescent leaves of Artemisia annua are one of the most active organs for overexpression of artemisinin biosynthesis responsible genes upon burst of singlet oxygen.

!To dissect and penetrate complexicity regarding the tissue-specific and environment-induced expression modes of cytosolic and plastidial terpene biosynthetic genes in A.annua, corresponding mRNAs relevant to terpene biosynthesis were quantitatively compared among distinctive organs and during different growth stages. Although all examined mRNAs gradually elevate from June to August in tested organs, a putative artemisinin biosynthesis responsible DBR2 mRNA represents the most abundant transcript anyplace and anytime. Apart from others, senescent leaves endow global activation of artemisinin biosynthetic genes and ultimately lead to enhanced artemisinin production. Direct measurement of 1 O2