ABA; drought stress; metabolite profiling; malate-starch; Arabidopsis thaliana; Blue light; guard cells; sucrose
Guo Woei Jiun, Nagy Reka, Chen Hsin-Yi, Pfrunder Stefanie, Yu Ya-Chi, Santelia Diana, Frommer Wolf B., Martinoia Enrico (2014), SWEET17, a facilitative transporter, mediates fructose transport across the tonoplast of Arabidopsis roots and leaves., in Plant Physiology
, 164(2), 777-789.
Seung David, Thalmann Matthias, Sparla Francesca, Achem Maher Abou, Lee Sang Kyu, Issakidis-Bourguet Emmanuelle, Svensson Birte, Zeeman Samuel Christian, Santelia Diana (2013), Arabidopsis thaliana AMY3 is a unique redox-regulated chloroplastic a-amylase, in Journal of Biological Chemistry
, 288(47), 33620-33633.
Meekins A. David, Guo Hou-Fu, Husodo Satrio, Paasch Bradley C., Bridges Travis M., Santelia Diana, Kötting Oliver, Vander Kooi Craig W., Gentry Matthew S. (2013), Structure of the Arabidopsis glucan phosphatase LIKE SEX FOUR2 reveals a unique mechanism for starch dephosphorylation, in Plant Cell
, 25(6), 2302-2314.
In recent years, there have been major advances in our understanding of starch metabolism in mesophyll cells, whereas very little is known in guard cells. In the current view, storage and mobilization of starch in guard cells follow an opposite rhythm with respect to mesophyll cells. Starch is present in darkness in almost all guard cell chloroplasts and is degraded in the light to provide carbon precursors for malate synthesis in the cytosol, thus compensating the positively charged potassium accumulation when stomata are open. Yet, this process represents a controversial point in the field, especially for Arabidopsis thaliana where the presence of starch in guard cells at the end of the dark period has been questioned. To shed more light on this issue, I have analyzed starch accumulation pattern in Arabidopsis wild type guard cells, providing already good evidence that starch is indeed present at the end of the night and seems to be degraded during the light period. The closure of stomata in response to water deficit represents an effective way to prevent excessive water loss, thus making guard cells a putative target to engineer drought avoidance in plants with minimal alterations of yield. Notably, during my screen of Arabidopsis starch-related mutants for drought stress tolerance, I have found that loss of functional b-amylase 1 (BAM1) confers drought resistance. This finding is in agreement with the observation that bam1 mutants have reduced stomatal opening compared to the wild type, most likely due to the elevated starch amounts in the guard cells. The fact that impairment of starch degradation in guard cells results in drought stress tolerance opens new exciting hypothesis about the function of starch in guard cells during water stress responses. The aim of the proposed research is to employ molecular and biochemical approaches to investigate the cellular mechanisms of starch breakdown in Arabidopsis guard cells and to identify the key factors required to trigger starch degradation at the onset of light. I also propose to investigate how the stress-induced reprogramming of carbon partitioning is affecting malate and/or sucrose metabolism in guard cells, and what consequences might have on stomatal behavior. I am confident that the proposed investigations will have the potential to improve our understanding of guard cell carbon metabolism, leading to the identification of new key targets for genetic engineering of stress tolerance to drought stress. With the knowledge we will gain from the model plant Arabidopsis thaliana, it will be possible to move forward with research and rapidly initiate improvements in plants of economic importance.