期刊
PHOTOSYNTHESIS RESEARCH
卷 142, 期 1, 页码 69-85出版社
SPRINGER
DOI: 10.1007/s11120-019-00649-2
关键词
Chlorophyll breakdown; Chlorophyll turnover; PAO/phyllobilin pathway; Pheophytin; Phyllobilin; Photosystem II repair
资金
- Austrian Science Fund (FWF) [P-28522]
- Swiss National Foundation [31003A_172977]
- Swiss National Science Foundation (SNF) [31003A_172977] Funding Source: Swiss National Science Foundation (SNF)
- Austrian Science Fund (FWF) [P28522] Funding Source: Austrian Science Fund (FWF)
Chlorophyll (Chl) breakdown is a diagnostic visual process of leaf senescence, which furnishes phyllobilins (PBs) by the PAO/phyllobilin pathway. As Chl breakdown disables photosynthesis, it appears to have no role in photoactive green leaves. Here, colorless PBs were detected in green, non-senescent leaves of Arabidopsis thaliana. The PBs from the green leaves had structures entirely consistent with the PAO/phyllobilin pathway and the mutation of a single Chl catabolic enzyme completely abolished PBs with the particular modification. Hence, the PAO/phyllobilin pathway was active in the absence of visible senescence and expression of genes encoding Chl catabolic enzymes was observed in green Arabidopsis leaves. PBs accumulated to only sub-% amounts compared to the Chls present in the green leaves, excluding a substantial contribution of Chl breakdown from rapid Chl turnover associated with photosystem II repair. Indeed, Chl turnover was shown to involve a Chl a dephytylation and Chl a reconstitution cycle. However, non-recyclable pheophytin a is also liberated in the course of photosystem II repair, and is proposed here to be scavenged and degraded to the observed PBs. Hence, a cryptic form of the established pathway of Chl breakdown is indicated to play a constitutive role in photoactive leaves.
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