Energy-rich molecules produced by photosynthesis feed our planet. The majority of these substances are moved from the sites of assimilation in the plants (sources) to distant tissues for growth, energy conversion, and/or storage (sinks). Photoassimilate translocation in plants takes place in the phloem. An estimated 90% of the food we consume has been translocated through this tissue. The phloem is also the target for an armada of pests such as aphids and leafhoppers, and plant viruses use it for systemic infection. Therefore the phloem is of fundamental importance for food security, impact of climate change on plant performance, and the development of bio-energy crops. Unfortunately, the complexity of the phloem tissue and the notorious problems it causes for cell biological investigations have left us with many open questions regarding its basic functions including the mechanism of translocation, allocation of assimilates, and plant pathogen interactions. Our group has developed a variety of techniques to investigate the secrets of the least understood major tissue type in plants. Current projects include:
A) Proteomics of sieve elements.
Sieve elements are the functional (transporting) units of the phloem. Their cell biology is quite unique in that they lose many of their organelles including the nucleus but retain a few specific organelles whose function is basically unknown. So far, omics approaches have been hampered by the lack of protocols for sieve element separation from the neighboring cells. We recently developed a method to isolate sieve elements, from which we expect major advances in our understanding of phloem function and protein interactions with plant pathogens.
B) Phloem unloading
The process of phloem unloading allows plants to generate energy-rich organs such as fruits, storage roots, cereals, tubers etc., which are our major food sources. The mechanisms of phloem unloading are poorly understood. We made significant progress by developing microscopy techniques for in situ observations of solutes exiting the phloem. We discovered unique funnel-shaped plasmodesmata which control the exit of solutes. Currently we work on principles of exit control which in the future may allow us to direct flow to specific sinks of interest.
C) Many other interesting things such as:
– engineering of plants for phytoremediation
– the role of cell wall swelling on plant cell biology
– the cell biology and physiology of giant kelp
– any kind of basic principles of plant cell biology / physiology