Unit of Plant Physiology and Molecular Biology, University of Turku


Plant Virus Projects                              

Project leader: Kirsi Lehto, Ph.D.
phone: +358 2 333 6266 (Turku)
email: klehto@utu.fi


1. Effects of viral rna-silencing suppressors on plant systemic cell biology, and on plant responses to viral infections

Arto Soitamo (post-doctoral fellow), Shahid Siddique (post-doctoral fellow), Balaji Jada (graduate student)


Project description:

In the past years we have produced a set of transgenic Nicotiana tabacum and N. bentahamiana plants which express well-characterized silencing suppressors derived from six different virus families (P1 of Rice yellow mosaic sobemovirus (RYMV), P19 of Tomato bushy stunt virus, P25 of Potato virus X, HcPro of Potato virus Y, 2b of Cucumber mosaic cucumovirus, AC2 of African cassava mosaic geminivirus). The aim for the production of this large collection of transgenic plants, in two different Nicotiana species has been to compare, side by side, the functions of these silencing suppressors in isogenic tobacco lines. Silencing suppressor-related plant phenotypes and the underlying gene expression alterations, and their interference with the plant-virus interactions are to be studied. The plants have been initially characterized, and their reactions to some virus infections have been analysed (Siddiqui et al. 2007, 2008 and unpublished results). Currently we are further analysing these plants to elucidate the following questions:

1. How these silencing suppressors interfere with the silencing pathways, and with the tissue-specific transcriptome of the two Nicotiana hosts. In addition to the expression profiles of the protein coding genes, also the accumulation patterns of different small RNAs will be analysed. 

2. Some silencing suppressors are known to affect the plants’ susceptibility to some heterologous viruses, affecting either their local accumulation or systemic spread in the hosts. Here we will analyse how these silencing suppressors interfere with the cell-to-cell and systemic spread of selected viruses. 

3. It is known that the silencing pathways, or the viral silencing suppressors may interact with the Salicylic acid (SA) or Pectin methyl esterase (PME) induced resistance reactions in plants. Here we aim to analyse these interactions to find out the cause and effect relationships between these inter-connected defence pathways.


These approaches will help to resolve how the RNA silencing pathways interfere with total plant transcriptome in two closely related Nicotiana species, how the viral silencing suppressors interfere with the silencing machinery, and how these together affect the spread and accumulation of different plant viruses. These investigations will promote the understanding of the role and significance of RNA silencing and of viral silencing suppressors in systemic cell biology, signalling and defence mechanisms.







2. Culturing Cyanobacteria with resources available on Mars

Participants and collaborators:
Pirkko Mäenpää, Harry Lehto.  Collaboration with the ESA-coordinated MELiSSA project, and the GESSE  (Geomicrobiology in Space Settlement and Exploration)


Project description:

With the anticipation of manned missions to Mars, different means for the production of different life support supplies (oxygen, food and fresh water) for the crews are needed. Long-duration mission to Mars will require high total amount of the supplies, and therefore replenishment of the life-support supplies from the local Martian resources would be very useful. Water, carbon dioxide and sun light are available on the Martian surface, and these could be converted, via photosynthesis process, into oxygen and edible carbohydrates (food). Higher crop plants would be most optimal for food production, but also lower photosynthetic organisms, such as cyanobacteria, could be used to produce oxygen both for the crew and the higher plants. In addition, edible cyanobacterial species, such as spirulina, would provide beneficial components to crew nutrition. More over, various cyanobacterial species could be used as the pioneer colonizers on Martian regolith, to induce active weathering, and release of nutrients from the rocky substrate. These would be needed further on as growth substrates for the higher plants. 


On the Martian surface any photosynthetic organisms would need to be cultured in enclosed condition to protect them from the external conditions, i.e. desiccation caused by the very low air pressure and the harsh UV and ionizing radiation, and also to prevent their escape to the environment. In technical terms it would be most beneficial to maintain the contained cultures as close as possible to the external conditions, at least to avoid large differences between internal and external air pressures. Still, all photosynthetic organisms have specific minimal requirements for suitable growth parameters, and also the quality of the produced biomass depends on the growth conditions to some extend. We are testing the growth potential of various cyanobacterial species, Synechocystis sp. and Synechococcus, Anabaena and of the edible cyanobacterium Arthrospira (spirulina) in different combinations of reduced air pressures and increased CO2 concentrations, and using various regolith extracts, to test the minimal combinations which support strong cell growth.  We are also analysing how these conditions affect the chemical composition of the cultured biomass.



List of publications

Last updated 1.2.2010