Present address: Department of Biology, West Virginia University, PO Box 6057, Morgantown, WV 26506, USA
Arabidopsis myrosinases TGG1 and TGG2 have redundant function in glucosinolate breakdown and insect defense
Article first published online: 4 APR 2006
The Plant Journal
Volume 46, Issue 4, pages 549–562, May 2006
How to Cite
Barth, C. and Jander, G. (2006), Arabidopsis myrosinases TGG1 and TGG2 have redundant function in glucosinolate breakdown and insect defense. The Plant Journal, 46: 549–562. doi: 10.1111/j.1365-313X.2006.02716.x
- Issue published online: 4 APR 2006
- Article first published online: 4 APR 2006
- Received 23 September 2005; revised 13 December 2005; accepted 6 January 2006.
In Arabidopsis and other Brassicaceae, the enzyme myrosinase (β-thioglucoside glucohydrolase, TGG) degrades glucosinolates to produce toxins that deter herbivory. A broadly applicable selection for meiotic recombination between tightly linked T-DNA insertions was developed to generate Arabidopsis tgg1tgg2 double mutants and study myrosinase function. Glucosinolate breakdown in crushed leaves of tgg1 or tgg2 single mutants was comparable to that of wild-type, indicating redundant enzyme function. In contrast, leaf extracts of tgg1tgg2 double mutants had undetectable myrosinase activity in vitro, and damage-induced breakdown of endogenous glucosinolates was apparently absent for aliphatic and greatly slowed for indole glucosinolates. Maturing leaves of myrosinase mutants had significantly increased glucosinolate levels. However, developmental decreases in glucosinolate content during senescence and germination were unaffected, showing that these processes occur independently of TGG1 and TGG2. Insect herbivores with different host plant preferences and feeding styles varied in their responses to myrosinase mutations. Weight gain of two Lepidoptera, the generalist Trichoplusia ni and the facultative Solanaceae-specialist Manduca sexta, was significantly increased on tgg1tgg2 double mutants. Two crucifer-specialist Lepidoptera had differing responses. Whereas Plutella xylostella was unaffected by myrosinase mutations, Pieris rapae performed better on wild-type, perhaps due to reduced feeding stimulants in tgg1tgg2 mutants. Reproduction of two Homoptera, Myzus persicae and Brevicoryne brassicae, was unaffected by myrosinase mutations.