期刊
BIOCHEMICAL JOURNAL
卷 477, 期 17, 页码 3237-3252出版社
PORTLAND PRESS LTD
DOI: 10.1042/BCJ20200480
关键词
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资金
- U.S. Department of Energy [DE-FG02-91ER2002]
- Great Lakes Bioenergy Research Center, U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research [DE-SC0018409]
- U.S. National Science Foundation
- Michigan AgBioResearch
Feeding (CO2)-C-14 was crucial to uncovering the path of carbon in photosynthesis. Feeding (CO2)-C-13 to photosynthesizing leaves emitting isoprene has been used to develop hypotheses about the sources of carbon for the methylerythritol 4-phosphate pathway, which makes the precursors for terpene synthesis in chloroplasts and bacteria. Both photosynthesis and isoprene studies found that products label very quickly (<10 min) up to 80-90% but the last 10-20% of labeling requires hours indicating a source of C-12 during photosynthesis and isoprene emission. Furthermore, studies with isoprene showed that the proportion of slow label could vary significantly. This was interpreted as a variable contribution of carbon from sources other than the Calvin-Benson cycle (CBC) feeding the methylerythritol 4-phosphate pathway. Here, we measured the degree of label in isoprene and photosynthetic metabolites 20 min after beginning to feed (CO2)-C-13. Isoprene labeling was the same as labeling of photosynthesis intermediates. High temperature reduced the label in isoprene and photosynthesis intermediates by the same amount indicating no role for alternative carbon sources for isoprene. A model assuming glucose, fructose, and/or sucrose reenters the CBC as ribulose 5-phosphate through a cytosolic shunt involving glucose 6-phosphate dehydrogenase was consistent with the observations.
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