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Plant Cell Advance Publication. Published on December 16, 2016, doi:10.1105/tpc.16.00950
IN BRIEF
It was a Great, Green Year: Identification of a Chlorophyll Dephytylase That Functions in Chlorophyll Turnover
Green may have been the Pantone Color of
the
Year
for
2013
(http://www.pantone.com/color-of-the-year2013), but 2016 was a great year for papers
on chlorophyll research, at The Plant Cell and
beyond. In this year, we saw a pile of
interesting papers examining chlorophyll
degradation,
including
its
regulatory
mechanisms. For example, to identify
transcription factors upstream of the key
enzyme pheophorbide a oxygenase (PAO),
which is a rate-limiting factor in chlorophyll
breakdown, Ghandchi and co-authors (2016)
used regression modeling and correlation
analysis to look for factors that co-expressed
with PAO under a variety of environmental
conditions. They identified a correlation with
specific transcription factors and a regulatory
network that integrates stimuli from abiotic
stresses (such as freezing and drought) and
senescence to modulate specific transcription
factors that control expression of PAO and
other genes, and thus regulate chlorophyll
breakdown.
In another paper that generated some
discussion, Wu and co-authors (2016) report
that
NON-YELLOWING2/STAY-GREEN2
(NYE2/SGR2), a close homolog of
SGR/NYE1 (Mendel’s green cotyledon gene)
functions as a positive regulator of chlorophyll
breakdown and present several observations
that are inconsistent with results from
Sakuraba et al. (2014), specifically regarding
the phenotypes of nye1 nye2 double mutants,
which Wu et al. found to have a strong staygreen phenotype. These discrepancies,
possibly due to growth conditions or genetic
effects, and the role of NYE2/SGR2 await
further clarification.
Enzymes also received a bit of attention
in 2016, with the discovery of several missing
links in the chlorophyll breakdown pathway
(figure). For example, Shimoda et al. revealed
that STAY-GREEN (SGR) functions as a
magnesium dechelatase, which converts
chlorophyll a to pheophytin a and also
functions in degradation of the photosystems.
Further along the chlorophyll breakdown
pathway, Hauenstein and co-authors found an
unexpected role for the chloroplast protein
TRANSLOCON
AT
THE
INNER
CHLOROPLAST ENVELOPE 55 (TIC55) in
the degradation of phyllobilins. TIC55 had
been implicated in redox-regulated protein
import in the chloroplast, making this finding
surprising.
To cap off this year, in the December
issue of The Plant Cell, Lin et al., (2016)
report the exciting, somewhat serendipitous
discovery of another missing enzyme, the
activity that removes chlorophyll’s phytol tail
during chlorophyll turnover. The authors
started their research by examining a semidominant mutant that produces a heatsensitive phenotype and ended up identifying
CHLOROPHYLL DEPHYTYLASE1 (CLD1).
After cloning the locus responsible for the
mutant phenotype, the authors speculated
that the encoded enzyme might act on
chlorophyll, based on its conservation and
similarity to pheophytinase (PPH, see figure),
particularly in the active site region. In vitro
assays showed that CLD1 can dephytylate
chlorophyll a and b, and pheophytin a, and
that the mutant protein had higher activity
than wild-type CLD1. Excess CLD1 activity
caused mutant plants to accumulate
chlorophyllides after heat shock and
suppression of CLD1 by an artificial micro
RNA also caused plants to be sensitive to
heat stress, with damage to Photosystem II,
indicating the importance of chlorophyll
turnover in photosystem stability.
Pantone might choose puce or magenta
as the color of the year for 2017, but at The
Plant Cell, we choose green every year.
Here’s to another great, green year!
Jennifer Mach
Science Editor
[email protected]
ORCID ID: 0000-0002-1141-6306
REFERENCES
Ghandchi, F.P., Caetano-Anolles, G.,
Clough, S.J., Ort, D.R. (2016) Investigating
the Control of Chlorophyll Degradation by
Genomic Correlation Mining PLOS ONE
10.1371/journal.pone.0162327
Hauenstein, M., Christ, B., Das, A., Aubry,
S., and Hörtensteiner, S. (2016) A role for
TIC55 as a hydroxylase of phyllobilins, the
products of chlorophyll breakdown during
plant
senescence.
Plant
Cell
Chlorophyll breakdown. Pathways in breakdown of chlorophyll. The dephytylase
identified by Lin et al. is shown in red; other enzymes mentioned are shown in blue. Please
see text and Lin et al. for other abbreviations. [Reprinted and modified from Lin et al., 2016;
Figure 9].
©2016 American Society of Plant Biologists. All Rights Reserved
10.1105/tpc.16.00630.
Lin, Y.-P., Wu, M.-C., and Charng, Y.-y.
(2016) Identification of Chlorophyll
Dephytylase Involved in Chlorophyll
Turnover in Arabidopsis Plant Cell
10.1105/tpc.16.00478.
Sakuraba, Y., Park, S.Y., Kim, Y.S., Wang,
S.H., Yoo, S.C., Hortensteiner, S., and
Paek,
N.C.
(2014).
Arabidopsis
STAYGREEN2 is a negative regulator of
chlorophyll degradation during leaf
senescence. Mol. Plant 7:1288–1302.
Shimoda, Y., Ito, H., and Tanaka, A. (2016)
Arabidopsis STAY-GREEN, Mendel’s green
cotyledon gene, encodes magnesiumdechelatase.
Plant
Cell
10.1105/tpc.16.00428.
Wu, S., Li, Z., Yang, L., Xie, Z., Chen, J.,
Zhang, W., Liu, T., Gao, S., Gao, J., Zhu,
Y., Xin, J., Ren, G., and Benke Kuai, B.
(2016) NON-YELLOWING2 (NYE2), a
Close Paralog of NYE1, Plays a Positive
Role in Chlorophyll Degradation in
Arabidopsis
Molecular
Plant
10.1016/j.molp.2015.12.016.
Parsed Citations
Ghandchi, F.P., Caetano-Anolles, G., Clough, S.J., Ort, D.R. (2016) Investigating the Control of Chlorophyll Degradation by
Genomic Correlation Mining PLOS ONE 10.1371/journal.pone.0162327
Pubmed: Author and Title
CrossRef: Author and Title
Google Scholar: Author Only Title Only Author and Title
Hauenstein, M., Christ, B., Das, A., Aubry, S., and Hörtensteiner, S. (2016) A role for TIC55 as a hydroxylase of phyllobilins, the
products of chlorophyll breakdown during plant senescence. Plant Cell 10.1105/tpc.16.00630.
Pubmed: Author and Title
CrossRef: Author and Title
Google Scholar: Author Only Title Only Author and Title
Lin, Y.-P., Wu, M.-C., and Charng, Y.-y. (2016) Identification of Chlorophyll Dephytylase Involved in Chlorophyll Turnover in
Arabidopsis Plant Cell 10.1105/tpc.16.00478.
Pubmed: Author and Title
CrossRef: Author and Title
Google Scholar: Author Only Title Only Author and Title
Sakuraba, Y., Park, S.Y., Kim, Y.S., Wang, S.H., Yoo, S.C., Hortensteiner, S., and Paek, N.C. (2014). Arabidopsis STAYGREEN2 is a
negative regulator of chlorophyll degradation during leaf senescence. Mol. Plant 7:1288-1302.
Pubmed: Author and Title
CrossRef: Author and Title
Google Scholar: Author Only Title Only Author and Title
Shimoda, Y., Ito, H., and Tanaka, A. (2016) Arabidopsis STAY-GREEN, Mendel's green cotyledon gene, encodes magnesiumdechelatase. Plant Cell 10.1105/tpc.16.00428.
Pubmed: Author and Title
CrossRef: Author and Title
Google Scholar: Author Only Title Only Author and Title
Wu, S., Li, Z., Yang, L., Xie, Z., Chen, J., Zhang, W., Liu, T., Gao, S., Gao, J., Zhu, Y., Xin, J., Ren, G., and Benke Kuai, B. (2016) NONYELLOWING2 (NYE2), a Close Paralog of NYE1, Plays a Positive Role in Chlorophyll Degradation in Arabidopsis Molecular Plant
10.1016/j.molp.2015.12.016.
Pubmed: Author and Title
CrossRef: Author and Title
Google Scholar: Author Only Title Only Author and Title
It was a Great, Green Year: Identification of a Chlorophyll Dephytylase That Functions in
Chlorophyll Turnover
Jennifer Mach
Plant Cell; originally published online December 16, 2016;
DOI 10.1105/tpc.16.00950
This information is current as of June 16, 2017
Supplemental Data
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