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Brassica rapa plants adapted to microgravity with reduced photosystem I and its photochemical activityThe photosynthetic apparatus contains several protein complexes, many of which are regulated by environmental conditions. In this study, the influences of microgravity on PSI and PSII in Brassica rapa plants grown aboard the space shuttle were examined. We found that Brassica plants grown in space had a normal level of growth relative to controls under similar conditions on Earth. Upon return to Earth, cotyledons were harvested and thylakoid membranes were isolated. Analysis of chlorophyll contents showed that the Chl a/b ratio (3.5) in flight cotyledons was much higher than a ratio of 2.42 in the ground controls. The flight samples also had a reduction of PSI complexes and a corresponding 30% decrease of PSI photochemical activity. Immunoblotting showed that the reaction centre polypeptides of PSI were more apparently decreased (e.g. by 24-33% for PsaA and PsaB, and 57% for PsaC) than the light-harvesting complexes. In comparison, the accumulation of PSII complex was less affected in microgravity, thus only a slight reduction in D1, D2 and LHCII was observed in protein blots. However, there was a 32% decrease of OEC1 in the flight samples, indicating a defective OEC subcomplex. In addition, an average 54% increase of the 54 kDa CF1-beta isoform was found in the flight samples, suggesting that space-grown plants suffered from certain stresses, consistent with implications of the increased Chl a/b ratio. Taken together, the results demonstrated that Brassica plants can adapt to spaceflight microgravity, but with significant alterations in chloroplast structures and photosynthetic complexes, and especially reduction of PSI and its activity.
Document ID
20050193564
Acquisition Source
Kennedy Space Center
Document Type
Reprint (Version printed in journal)
Authors
Jiao, Shunxing
(Kansas State University Manhattan, KS 66506, United States)
Hilaire, Emmanuel
Paulsen, Avelina Q.
Guikema, James A.
Date Acquired
August 23, 2013
Publication Date
October 1, 2004
Publication Information
Publication: Physiologia plantarum
Volume: 122
Issue: 2
ISSN: 0031-9317
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NAG10-0142
CONTRACT_GRANT: NAGW-1197
CONTRACT_GRANT: NAGW-2328
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
STS-87 Shuttle Project
short duration
Flight Experiment
manned
NASA Discipline Plant Biology

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