@article{TenenboimSmirnovaWillmitzeretal.2014, author = {Tenenboim, Hezi and Smirnova, Julia and Willmitzer, Lothar and Steup, Martin and Brotman, Yariv}, title = {VMP1-deficient Chlamydomonas exhibits severely aberrant cell morphology and disrupted cytokinesies}, series = {BMC plant biology}, volume = {14}, journal = {BMC plant biology}, publisher = {BioMed Central}, address = {London}, issn = {1471-2229}, doi = {10.1186/1471-2229-14-121}, pages = {13}, year = {2014}, abstract = {Background: The versatile Vacuole Membrane Protein 1 (VMP1) has been previously investigated in six species. It has been shown to be essential in macroautophagy, where it takes part in autophagy initiation. In addition, VMP1 has been implicated in organellar biogenesis; endo-, exo- and phagocytosis, and protein secretion; apoptosis; and cell adhesion. These roles underly its proven involvement in pancreatitis, diabetes and cancer in humans. Results: In this study we analyzed a VMP1 homologue from the green alga Chlamydomonas reinhardtii. CrVMP1 knockdown lines showed severe phenotypes, mainly affecting cell division as well as the morphology of cells and organelles. We also provide several pieces of evidence for its involvement in macroautophagy.}, language = {en} } @article{MalinovaMahlowAlseekhetal.2014, author = {Malinova, Irina and Mahlow, Sebastian and Alseekh, Saleh and Orawetz, Tom and Fernie, Alisdair R. and Baumann, Otto and Steup, Martin and Fettke, J{\"o}rg}, title = {Double knockout mutants of arabidopsis grown under normal conditions reveal that the plastidial phosphorylase isozyme participates in transitory starch metabolism}, series = {Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants}, volume = {164}, journal = {Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants}, number = {2}, publisher = {American Society of Plant Physiologists}, address = {Rockville}, issn = {0032-0889}, doi = {10.1104/pp.113.227843}, pages = {907 -- 921}, year = {2014}, abstract = {In leaves of two starch-related single-knockout lines lacking either the cytosolic transglucosidase (also designated as disproportionating enzyme 2, DPE2) or the maltose transporter (MEX1), the activity of the plastidial phosphorylase isozyme (PHS1) is increased. In both mutants, metabolism of starch-derived maltose is impaired but inhibition is effective at different subcellular sites. Two constitutive double knockout mutants were generated (designated as dpe2-1 x phs1a and mex1 x phs1b) both lacking functional PHS1. They reveal that in normally grown plants, the plastidial phosphorylase isozyme participates in transitory starch degradation and that the central carbon metabolism is closely integrated into the entire cell biology. All plants were grown either under continuous illumination or in a light-dark regime. Both double mutants were compromised in growth and, compared with the single knockout plants, possess less average leaf starch when grown in a light-dark regime. Starch and chlorophyll contents decline with leaf age. As revealed by transmission electron microscopy, mesophyll cells degrade chloroplasts, but degradation is not observed in plants grown under continuous illumination. The two double mutants possess similar but not identical phenotypes. When grown in a light-dark regime, mesophyll chloroplasts of dpe2-1 x phs1a contain a single starch granule but under continuous illumination more granules per chloroplast are formed. The other double mutant synthesizes more granules under either growth condition. In continuous light, growth of both double mutants is similar to that of the parental single knockout lines. Metabolite profiles and oligoglucan patterns differ largely in the two double mutants.}, language = {en} } @article{HemmeVeyelMuehlhausetal.2014, author = {Hemme, Dorothea and Veyel, Daniel and Muehlhaus, Timo and Sommer, Frederik and Jueppner, Jessica and Unger, Ann-Katrin and Sandmann, Michael and Fehrle, Ines and Schoenfelder, Stephanie and Steup, Martin and Geimer, Stefan and Kopka, Joachim and Giavalisco, Patrick and Schroda, Michael}, title = {Systems-wide analysis of acclimation responses to long-term heat stress and recovery in the photosynthetic model organism Chlamydomonas reinhardtii}, series = {The plant cell}, volume = {26}, journal = {The plant cell}, number = {11}, publisher = {American Society of Plant Physiologists}, address = {Rockville}, issn = {1040-4651}, doi = {10.1105/tpc.114.130997}, pages = {4270 -- 4297}, year = {2014}, abstract = {We applied a top-down systems biology approach to understand how Chlamydomonas reinhardtii acclimates to long-term heat stress (HS) and recovers from it. For this, we shifted cells from 25 to 42 degrees C for 24 h and back to 25 degrees C for >= 8 h and monitored abundances of 1856 proteins/protein groups, 99 polar and 185 lipophilic metabolites, and cytological and photosynthesis parameters. Our data indicate that acclimation of Chlamydomonas to long-term HS consists of a temporally ordered, orchestrated implementation of response elements at various system levels. These comprise (1) cell cycle arrest; (2) catabolism of larger molecules to generate compounds with roles in stress protection; (3) accumulation of molecular chaperones to restore protein homeostasis together with compatible solutes; (4) redirection of photosynthetic energy and reducing power from the Calvin cycle to the de novo synthesis of saturated fatty acids to replace polyunsaturated ones in membrane lipids, which are deposited in lipid bodies; and (5) when sinks for photosynthetic energy and reducing power are depleted, resumption of Calvin cycle activity associated with increased photorespiration, accumulation of reactive oxygen species scavengers, and throttling of linear electron flow by antenna uncoupling. During recovery from HS, cells appear to focus on processes allowing rapid resumption of growth rather than restoring pre-HS conditions.}, language = {en} } @article{CisekTokarzKrouglovetal.2014, author = {Cisek, Richard and Tokarz, Danielle and Krouglov, Serguei and Steup, Martin and Emes, Michael J. and Tetlow, Ian J. and Barzda, Virginijus}, title = {Second harmonic generation mediated by aligned water in starch granules}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {118}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {51}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/jp508751s}, pages = {14785 -- 14794}, year = {2014}, abstract = {The origin of second harmonic generation (SHG) in starch granules was investigated using ab initio quantum mechanical modeling and experimentally examined using polarization-in, polarization-out (PIPO) second harmonic generation microscopy. Ab initio calculations revealed that the largest contribution to the SHG signal from A- and B-type allomorphs of starch originates from the anisotropic organization of hydroxide and hydrogen bonds mediated by aligned water found in the polymers. The hypothesis was experimentally tested by imaging maize starch granules under various hydration and heat treatment conditions that alter the hydrogen bond network. The highest SHG intensity was found in fully hydrated starch granules, and heat treatment diminished the SHG intensity. The PIPO SHG imaging showed that dried starch granules have a much higher nonlinear optical susceptibility component ratio than fully hydrated granules. In contrast, deuterated starch granules showed a smaller susceptibility component ratio demonstrating that SHG is highly sensitive to the organization of the hydroxyl and hydrogen bond network. The polarization SHG imaging results of potato starch granules, representing starch allomorph B, were compared to those of maize starch granules representing allomorph A. The results showed that the amount of aligned water was higher in the maize granules. Nonlinear microscopy of starch granules provides evidence that varying hydration conditions leads to significant changes in the nonlinear susceptibility ratio as well as the SHG intensity, supporting the hypothesis from ab initio calculations that the dominant contribution to SHG is due to the ordered hydroxide and hydrogen bond network.}, language = {en} } @misc{CencilNitschkeSteupetal.2014, author = {Cencil, Ugo and Nitschke, Felix and Steup, Martin and Minassian, Berge A. and Colleoni, Christophe and Ball, Steven G.}, title = {Transition from glycogen to starch metabolism in Archaeplastida}, series = {Trends in plant science}, volume = {19}, journal = {Trends in plant science}, number = {1}, publisher = {Elsevier}, address = {London}, issn = {1360-1385}, doi = {10.1016/j.tplants.2013.08.004}, pages = {18 -- 28}, year = {2014}, abstract = {In this opinion article we propose a scenario detailing how two crucial components have evolved simultaneously to ensure the transition of glycogen to starch in the cytosol of the Archaeplastida last common ancestor: (i) the recruitment of an enzyme from intracellular Chlamydiae pathogens to facilitate crystallization of alpha-glucan chains; and (ii) the evolution of novel types of polysaccharide (de)phosphorylating enzymes from preexisting glycogen (de)phosphorylation host pathways to allow the turnover of such crystals. We speculate that the transition to starch benefitted Archaeplastida in three ways: more carbon could be packed into osmotically inert material; the host could resume control of carbon assimilation from the chlamydial pathogen that triggered plastid endosymbiosis; and cyanobacterial photosynthate export could be integrated in the emerging Archaeplastida.}, language = {en} }