The survival strategy of parasitic plants is based on the rapid penetration of host plant tissue and the subsequent formation of physical connections (haustoria) with the host's vascular tissue. The prerequisite for this is that parasitic plants are equipped with a highly active enzyme set for the hydrolysis host plant cell walls. One project aims at characterizing secreted proteins of Cuscuta reflexa and identify enzymes with high cellulose and pectin degrading activiy. Identified enzymes are then structurally and functionally compared to counterparts from other plant-degrading organisms.
Using the tools that we developed for this, we can now also approach the question how attack and defence reactions between parasite and host are orchestrated.
|Cuscuta on pelargonium|
Photosynthesis is one of the hallmarks of plant life and is the most fundamental biochemical process on Earth. Photosynthesis is generally associated with cyanobacteria, alge and plants. A group of plants have, however, abandoned the photosynthetic life style and live from the organic and inorganic nutrients they can ”steal” from other plants. These parasites attach to the roots of their hosts or wind around the stems and leaves (see photos).
Parasitic plants have developed some morphological and metabolic traits that are closely connected to their parasitic lifestyle. They lack, for example, visible roots and leaves and have instead developed organs that are specialized in penetrating the tissue of their host plants.on earth. Photosynthesis
is generally associated with cyanobacteria, alge and plants. A group of plants have, however, abandoned the photosynthetic life style and live from the organic and inorganic nutrients they can ”steal” from other plants. These parasites attach to the roots of their hosts or wind around the stems and leaves (see photos).
These organs, are called haustoria. Finger-like absorbing hyphae at the tips of these haustoria extend into the
host’s vascular tissue and help in supplying the parasite with nutients (see photos).
Plant cell wall degradation by parasitic plants
In order to enable parasitic plants to rapidly penetrate lignified and unlignified tissue they produce a highly active enzyme set for the hydrolysis host plant cell walls. Our research in this field is concentrating on the following questions:
- Which enzymes are responsible for the high cellulolytic activity of Cuscuta during host infection?
- Is the same enzyme set used for modifying its own cell walls during rapid growth periods? If yes, how is the activity in different tissues regulated?
- Can enzymes from Cuscuta be used (alone or with others) for improving the efficiency of biofuels production?
We are using classical biochemical methods as well as modern transcriptomic and proteomic approaches to answer these questions.
|Cuscuta callus forming shoots|
Infection and immunity strategies
So far, very little is known about how parastitic plants are perceived by other plants and how they, in return, manage to evade defence responses. We have established sterile callus and shoot cultures of Cuscuta and built up an EST database plus full length dDNA library from two Cusctua species and hope that these will help usin order to assist in tackling thesse interesting questions.