NEWS FROM
PHYSIOLOGIA PLANTARUM
 |
 |
Published monthly on behalf of SPPS by Wiley-Blackwell.
 |
|
|
|
 |
Strawberries with ethylene
|
It is the right season for strawberries and they should be enjoyed with lots of fresh cream - and ethylene. A strawberry is a very peculiar fruit as the fleshy part is derived from the non-ovarian receptacle tissue, and it has been postulated that ripening of strawberries was not dependent on ethylene. But Pietro Iannetta from Scottish Crop Research Institute and co-workers show in a careful study that ethylene is certainly important for fruit development. Using laser photoacoustic spectroscopy they demonstrated diurnal fluctuations in ethylene production during ripening and a continuously increasing production in red, mature berries.
Read full article free: Iannetta et al (June 2006) Physiologia Plantarum 127: 247-259
|
|
NEWS IN BRIEF
FROM OTHER JOURNALS
|
|
Ancient Figs Beat Record for Human Agriculture
|
|
Source: Kislev et al (2 June 2006) Science 312: 1372-1374
|
|
|
|
Enzymes Spice Up Plant Scent
|
|
Source: Koeduka et al (12 June 2006) PNAS doi:10.1073/pnas.0603732103
|
|
|
|
|
|
|
Scandinavian research institute:
TRAP LABS (Transport Physiology Laboratories), Copenhagen
|
| |
|
|
Nutrient transport takes place all over the plant. Illustration courtesy of Michael G. Palmgren.
|
|
|
Fundamental to all plants is the ability to take up nutrients from the soil and transport them along with other solutes to whatever part of the plant they are needed. At TRAP LABS, these basic physiological processes have been the focus for intense research since Michael Gjedde Palmgren joined KVL (The Royal Veterinary and Agricultural University) as a Professor in 1998.
TRAP LABS makes up the bigger part of the Plant Physiology and Anatomy Laboratory, which belongs to the Department of Plant Biology at KVL in Copenhagen. They work in close cooperation with the group of Jan K. Schjørring who is Professor in plant nutrition at the university's Department of Agricultural Sciences.
So in order to complete the scientific expertise, Professor Alexander Schulz joined the lab just one year later from a position at Kiel University. With all together more than 40 peer-reviewed publications in journals as creditable as Science, he brought to the lab excellence in transport through plasmodesmata and the phloem.
| |  | | Non-invasive bioimaging reveals cytoplasmic streaming in real time. From www.trap.kvl.dk | |
Alexander Schulz makes intensive use of advanced bioimaging techniques for his studies and he is leader of the KVL Bioimaging Center, that makes the technologies available for other researchers. Bioimaging allows for non-invasive studies of transport processes in intact, living plants by a combination of fluorescence tagging and confocal laser scanning microscopy. Cell-to-cell and long-distance transport is highly regulated processes and as such they are extremely sensitive to preparative manipulation by the scientists.
In confocal laser scanning microscopy, a tiny laser spot is focused on a defined image plane deep within the intact tissue. If a fluorescent probe, that has been introduced to the plant e.g. by genetic engineering of a fluorescent protein, is hit by the laser it becomes excited. Light is then emitted exclusively from this tiny spot and is detected by a photomultiplier. The laser scans the specimen like the electron beam in a TV monitor and each excitation is recorded as a pixel on a video screen. This reveals a real time image of the cellular distribution of the probe at exactly that moment.
Using these techniques, Alexander Schulz and his 7 group members have studied transport in the phloem and the plasmodesmata, i.e. the cytoplasmic bridges that connect neighbouring cells. In a recent publication, they have elucidated a decisive role for companion cells of the phloem in regulating turnover of exudate proteins, and they have developed a new technique, caged probes, for studying symplasmic transport by spatially controlled photoactivation of a fluorochrome.
| |
|
|
Two varieties of barley have very different tolerance to low manganese availability. Photo courtesy of Jan K. Schjørring.
|
|
|
The group of Jan K. Schjørring is working with nutrient acquisition and utilization of plants, and how mineral elements are used for their metabolism, interaction with the environment and for stress tolerance. He has been working at KVL since 1988 and has published more than 90 papers in peer-reviewed journals.
Recently, they have investigated why some plants are more tolerant to low manganese availability than others. By using a technique called online inductively coupled plasma-mass spectrometry, the root uptake of subnanomolar concentrations of manganese could be measured and compared between two varieties of barley. The results indicated that the most tolerant variety had a much more efficient manganese transport system in the roots and accordingly had a higher net uptake of the micronutrient.
In another publication in The Plant Journal earlier this year, Jan K. Schjørring and colleagues from Germany, France and the UK used antisense technology to demonstrate how potato plants can survive photorespiratory impairment. When production of ammonium during daytime was inhibited by antisensing serine hydroxymethyltransferase, the plant responded by activating glutamine and glutamate synthase during the night, leading to a time shift in ammonia assimilation.
| |
|
|
Yeast is a favoured model system for TRAP LABS. From www.trap.kvl.dk
|
|
|
Michael G. Palmgren and the 13 members of his team study the structure, function and regulation of so called P-type ATPases. This is a large group of membrane bound proteins that utilize ATP to actively pump cations in or out of cells. The first many years of his research were devoted to the proton (H+) pump but now he has extended the studies to also encompass calcium, heavy metal, phospholipid and other pumps.
The function of the various pumps is studied in transgenic plants, where expression of the corresponding gene has been knocked out or altered. Moreover, regulation of the plant pumps is analyzed by expressing them in yeast cells, where their activity can be easily monitored. Almost 20 years ago Michael G. Palmgren pioneered the field by developing protocols to solubilize active ATPases and reconstitute them in sealed 'inside-out' vesicles. This allowed for experimental modification, e.g. proteolytic cleavage, of the pumps and precise measurements of how this affected the pumping efficiency.
Using a combination of these techniques, the team at TRAP LABS was the first to elucidate how many P-type ATPases are regulated by autoinhibitory domains on the proteins themselves. E.g. the C-terminal of the H+-ATPase functions as a 'break' that can be released by binding to 14-3-3 proteins, whereas activation of the Ca2+-ATPase is controlled by the N-terminus and is modulated by the calcium/calmodulin complex.
| |
|
|
Pollen from mutant plants (D, F) fails to release and germinate. Photo courtesy of Michael G. Palmgren.
|
|
|
In another recent publication Michael G. Palmgren and his colleagues have been the first to study in a multicellular organism the function of an ATPase belonging to the P5 subfamily, which they were the first to describe in 1998. The protein appears to regulate the ionic status of compartments in secretory pathways, which in turn controls the trafficking of vesicle materiel to the plasma membrane. Knocking out this particular pump in Arabidopsis resulted in failure of pollen development and male infertility.
These research groups of Michael G. Palmgren, Alexander Schulz and Jan K. Schjørring have recently been selected for their expertise by The Danish National Research Foundation to apply for establishment of a centre of excellence in Plant Transport Biology.
You can find more information about TRAP LABS on its official website.
|
|
