Trichome Management to Enhance Camptothecins in Camptotheca Decaisne

Abstract

Inducible chemical defenses of plants have received much attention in the last three decades, and these defenses often involve trichomes. It is known that some plant secondary metabolites may accumulate in trichomes which can pro- tect plants from damage by herbivores. However, studies on plant trichomes are largely limited to some major vegetable or cash crops and model species with large glandular trichomes (e.g., Nictotiana and Arabidopsis). In fact, the existing studies on the effect of damage (pruning or defoliation) on trichome density or chemical production in plants are partial and even contradictory. strategies to maximize chemical induction in medicinal plants or pharmaceutical crops have not been developed well. Our experiments showed that camptothecins (CPTs) are primarily accumulated in glandular trichomes in Camptotheca. We found that pruning, particularly decapitation pruning (T-pruning) can effectively induce contents and derivatization of CPTs in Camptotheca, and the leveled CPTs caused induced endogenous autotoxic- ity (abnormal morphogenesis) in the plants. Auxin reduction is a trigging factor for such induced biosynthesis and en- dogenous autotoxicity. Because trichomes are visible to the naked eye and can be much more easily targeted and meas- ured than CPTs, the term Trichome Management is used for strategy development to induce CPTs in Camptotheca.