Non‐invasive, whole‐plant imaging of chloroplast movement and chlorophyll fluorescence reveals photosynthetic phenotypes independent of chloroplast photorelocation defects in chloroplast division mutants

Journal Article · Thu Oct 08 00:00:00 EDT 2015 · The Plant Journal

DOI:https://doi.org/10.1111/tpj.13009· OSTI ID:1401632

Dutta, Siddhartha ^[1]; Cruz, Jeffrey A. ^[2]; Jiao, Yuhua ^[3]; Chen, Jin ^[4]; Kramer, David M. ^[2]; Osteryoung, Katherine W. ^[1]

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1. Department of Plant Biology Michigan State University East Lansing MI 48824‐1312 USA
2. MSU‐DOE‐Plant Research Laboratory Michigan State University East Lansing MI 48824‐1312 USA, Department of Biochemistry and Molecular Biology Michigan State University East Lansing MI 48824‐1312 USA
3. MSU‐DOE‐Plant Research Laboratory Michigan State University East Lansing MI 48824‐1312 USA
4. MSU‐DOE‐Plant Research Laboratory Michigan State University East Lansing MI 48824‐1312 USA, Department of Computer Sciences and Engineering Michigan State University East Lansing MI 48824‐1312 USA

Summary Leaf chloroplast movement is thought to optimize light capture and to minimize photodamage. To better understand the impact of chloroplast movement on photosynthesis, we developed a technique based on the imaging of reflectance from leaf surfaces that enables continuous, high‐sensitivity, non‐invasive measurements of chloroplast movement in multiple intact plants under white actinic light. We validated the method by measuring photorelocation responses in Arabidopsis chloroplast division mutants with drastically enlarged chloroplasts, and in phototropin mutants with impaired photorelocation but normal chloroplast morphology, under different light regimes. Additionally, we expanded our platform to permit simultaneous image‐based measurements of chlorophyll fluorescence and chloroplast movement. We show that chloroplast division mutants with enlarged, less‐mobile chloroplasts exhibit greater photosystem  II photodamage than is observed in the wild type, particularly under fluctuating high levels of light. Comparison between division mutants and the severe photorelocation mutant phot1‐5 phot2‐1 showed that these effects are not entirely attributable to diminished photorelocation responses, as previously hypothesized, implying that altered chloroplast morphology affects other photosynthetic processes. Our dual‐imaging platform also allowed us to develop a straightforward approach to correct non‐photochemical quenching ( NPQ ) calculations for interference from chloroplast movement. This correction method should be generally useful when fluorescence and reflectance are measured in the same experiments. The corrected data indicate that the energy‐dependent ( qE ) and photoinhibitory ( qI ) components of NPQ contribute differentially to the NPQ phenotypes of the chloroplast division and photorelocation mutants. This imaging technology thus provides a platform for analyzing the contributions of chloroplast movement, chloroplast morphology and other phenotypic attributes to the overall photosynthetic performance of higher plants.

• Sponsoring Organization: USDOE
• OSTI ID: 1401632
• Journal Information: The Plant Journal, Journal Name: The Plant Journal Vol. 84 Journal Issue: 2; ISSN 0960-7412
• Publisher: Wiley-Blackwell
• Country of Publication: United Kingdom
• Language: English