TY  - JOUR
A1  - Cisek, Richard
A1  - Tokarz, Danielle
A1  - Kontenis, Lukas
A1  - Barzda, Virginijus
A1  - Steup, Martin
T1  - Polarimetric second harmonic generation microscopy
BT  - an analytical tool for starch bioengineering
JF  - Starch-Starke
N2  - Second harmonic generation (SHG) is a nonlinear optical process that inherently generates signal in non-centrosymmetric materials, such as starch granules, and therefore can be used for label-free imaging. Both intensity and polarization of SHG are determined by material properties that are characterized by the nonlinear susceptibility tensor, ((2)). Examination of the tensor is performed for each focal volume of the image by measuring the outgoing polarization state of the SHG signal for a set of incoming laser beam polarizations. Mapping of nonlinear properties expressed as the susceptibility ratio reveals structural features including the organization of crystalline material within a single starch granule, and the distribution of structural properties in a population of granules. Isolated granules, as well as in situ starch, can be analyzed using polarimetric SHG microscopy. Due to the fast sample preparation and short imaging times, polarimetric SHG microscopy allows for a quick assessment of starch structure and permits rapid feedback for bioengineering applications. This article presents the basics of SHG theory and microscopy applications for starch-containing materials. Quantification of ultrastructural features within individual starch granules is described. New results obtained by polarization resolved SHG microscopy of starch granules are presented for various maize genotypes revealing heterogeneity within a single starch particle and between various granules.
KW  - Determination of crystallinity
KW  - Determination of hydration
KW  - Label-free imaging
KW  - Nonlinear optical microscopy
KW  - Structural determination
Y1  - 2017
U6  - https://doi.org/10.1002/star.201700031
SN  - 0038-9056
SN  - 1521-379X
VL  - 70
IS  - 1-2
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Cencil, Ugo
A1  - Nitschke, Felix
A1  - Steup, Martin
A1  - Minassian, Berge A.
A1  - Colleoni, Christophe
A1  - Ball, Steven G.
T1  - Transition from glycogen to starch metabolism in Archaeplastida
JF  - Trends in plant science
N2  - 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.
KW  - evolution of plastids
KW  - starch and glycogen metabolism
KW  - polyglucan debranching reactions
KW  - starch and glycogen (de)phosphorylation
KW  - Chlamydia-like bacteria
KW  - Lafora disease
Y1  - 2014
U6  - https://doi.org/10.1016/j.tplants.2013.08.004
SN  - 1360-1385
VL  - 19
IS  - 1
SP  - 18
EP  - 28
PB  - Elsevier
CY  - London
ER  -