FZL is primarily localized to the inner chloroplast membrane however influences thylakoid maintenance.

KEY MESSAGE: FZL is primarily localized to the chloroplast inner envelope and not to the thylakoids, but nevertheless affects the maintenance of thylakoid membranes and photosynthetic protein complexes. The fuzzy-onion-like protein (FZL) is a membrane-bound dynamin-like GTPase located in the chloroplast. We have investigated the chloroplast sub-localization of the endogenous FZL protein and found it to be primarily localized to the inner envelope. Moreover, we observed that mature leaves of fzl mutants start to turn pale, especially in the midvein area of the leaves, 11 days after germination. We therefore assessed their photosynthetic performance as well as the accumulation of thylakoid membrane proteins and complexes after the initial appearance of the phenotype. Interestingly, we could observe a significant decrease in amounts of the cytochrome b6f complex in 20-day-old mutants, which was also reflected in an impaired electron transport rate as well as a more oxidized P700 redox state. Analysis of differences in transcriptome datasets obtained before and after onset of the phenotype, revealed large-scale changes in gene expression after the phenotype became visible. In summary, we propose that FZL, despite its localization in the inner chloroplast envelope has an important role in thylakoid maintenance in mature and aging leaves.

Analysis of Arabidopsis thaliana Growth Behavior in Different Light Qualities.

Plant biologists often need to observe the growth behavior of their chosen species. To this end, the plants need constant environmental and stable light conditions, which are preferably variable in quantity and quality so that studies under different setups can be conducted. These requirements are met by climatic chambers featuring light emitting diodes (LED) lights, which can - in contrast to fluorescent lights - be set to different wavelengths. LEDs are energy conserving and emit virtually no heat even at light intensities, which often constitutes a problem with other light sources. The presented protocol provides a step-by-step guidance of how to program a climatic chamber equipped with variable LED lights as well as describing several approaches for in depth analysis of growth phenotypes. Depending on the experimental set-up various characteristics of the growing plants can be observed and analyzed. Here we describe how to determine fresh weight, leaf area, photosynthetic activity, and stomatal density. We demonstrate that in order to obtain reliable data and draw valid conclusions it is mandatory to use a sufficient number of individuals for statistical evaluation. Taking too few plants for this kind of analysis results in high statistical errors and consequently in less clear interpretations of the data.

Comparative Phenotypical and Molecular Analyses of Arabidopsis Grown under Fluorescent and LED Light.

Comparative analyses of phenotypic and molecular traits of Arabidopsis thaliana grown under standardised conditions is still a challenge using climatic devices supplied with common light sources. These are in most cases fluorescent lights, which have several disadvantages such as heat production at higher light intensities, an invariable spectral output, and relatively rapid "ageing". This results in non-desired variations of growth conditions and lowers the comparability of data acquired over extended time periods. In this study, we investigated the growth behaviour of Arabidopsis Col0 under different light conditions, applying fluorescent compared to LED lamps, and we conducted physiological as well as gene expression analyses. By changing the spectral composition and/or light intensity of LEDs we can clearly influence the growth behaviour of Arabidopsis and thereby study phenotypic attributes under very specific light conditions that are stable and reproducible, which is not necessarily given for fluorescent lamps. By using LED lights, we can also roughly mimic the sun light emission spectrum, enabling us to study plant growth in a more natural-like light set-up. We observed distinct growth behaviour under the different light regimes which was reflected by physiological properties of the plants. In conclusion, LEDs provide variable emission spectra for studying plant growth under defined, stable light conditions.