ABSTRACT
Artemisia annua is the main natural source of artemisinin production. In A. annua, extended drought stress severely reduces its biomass and artemisinin production while short-term water-withholding or abscisic acid (ABA) treatment can increase artemisinin biosynthesis. ABA-responsive transcription factor AabZIP1 and JA signaling AaMYC2 have been shown in separate studies to promote artemisinin production by targeting several artemisinin biosynthesis genes. Here, we found AabZIP1 promote the expression of multiple artemisinin biosynthesis genes including AaDBR2 and AaALDH1, which AabZIP1 does not directly activate. Subsequently, it was found that AabZIP1 up-regulates AaMYC2 expression through direct binding to its promoter, and that AaMYC2 binds to the promoter of AaALDH1 to activate its transcription. In addition, AabZIP1 directly transactivates wax biosynthesis genes AaCER1 and AaCYP86A1. The biosynthesis of artemisinin and cuticular wax and the tolerance of drought stress were significantly increased by AabZIP1 overexpression, whereas they were significantly decreased in RNAi-AabZIP1 plants. Collectively, we have uncovered the AabZIP1-AaMYC2 transcriptional module as a point of cross-talk between ABA and JA signaling in artemisinin biosynthesis, which may have general implications. We have also identified AabZIP1 as a promising candidate gene for the development of A. annua plants with high artemisinin content and drought tolerance in metabolic engineering breeding.
ABSTRACT
Atropa belladonna L. is the officially medicinal plant species and the main commercial source of scopolamine and hyoscyamine in China. In this study, we reported the simultaneous overexpression of two functional genes involved in biosynthesis of scopolamine, which respectively encoded the upstream key enzyme putrescine N-methyltransferase (PMT; EC 2.1.1.53) and the downstream key enzyme hyoscyamine 6beta-hydroxylase (H6H; EC 1.14.11.11) in transgenic hair root cultures of Atropa belladonna L. HPLC results suggested that four transgenic hair root lines produced higher content of scopolamine at different levels compared with nontransgenic hair root cultures. And scopolamine content increased to 8.2 fold in transgenic line PH2 compared with that of control line; and the other four transgenic lines showed an increase of scopolamine compared with the control. Two of the transgenic hair root lines produced higher levels of tropane alkaloids, and the content increased to 2.7 fold in transgenic line PH2 compared with the control. The gene expression profile indicated that both PMT and H6H expressed at a different levels in different transgenic hair root lines, which would be helpful for biosynthesis of scopolamine. Our studies suggested that overexpression of A. belladonna endogenous genes PMT and H6H could enhance tropane alkaloid biosynthesis.
ABSTRACT
<p><b>OBJECTIVE</b>To study the variations of flavonoids contents in vine tips of sweetpotato (Ipomoea batatas) among different varieties, parts and the time of topping.</p><p><b>METHOD</b>The flavonoid contents in leaf, petiole and stem of vine tips at 6 different topping time of 3 varieties for vegetable-use Pushu 53, Guangcaishu No. 2 and Fushu 7-6, which were collected from Chongqing were determined by UV spectrophotometry with rutin as a standard substance.</p><p><b>RESULT</b>The results showed that the flavonoid content of Guangcaishu No. 2 was higher than that of Pusu 53, so was that of Pusu 53 than that of Fushu 7-6. The average flavonoid contents in leaf of 3 varieties were between 3.66 mg x L(-1) and 11.09 mg x L(-1) during 6 topping time, and those in petiole, stem were between 2.20-5.26 mg x L(-1) and 4.03-7.79 mg x L(-1), respectively. The rations of average flavonoid contents in leaf, petiole and stem to the total contents of vine tips among 3 varieties during their whole topping periods were 46.71%, 20.65% and 32.63%, respectively. The contents during earlier topping time were higher than those of later periods. The variance analysis of flavonoid contents revealed that there was significant difference between different varieties, parts and time of topping and significant interactions among varieties, parts and time of topping.</p><p><b>CONCLUSION</b>The results of the study indicate that the contents of flavonoid should be considered for the breeding, cultivation and industrialization of sweetpotato for vegetable-use.</p>