catches of Atlantic cod in the Gulf of Maine driven
partly by rapid ocean warming has contributed
to the collapse of the cod fisheries (24). In the
Gulf of Mexico, turnover of fish species in sea-grass assemblages as a result of species gains
and losses between the 1970s and 2000s have
been reported (25). In the Barent Sea, recent
warming since the early 2000s has resulted in
northward retraction of Arctic fish communities (e.g., bigeye sculpin and Greenland halibut)
but expansion of the sub-Arctic and temperate
communities (e.g., Atlantic cod and haddock)
(26). The projected changes to fisheries estimated from our study under the 3.5°C warming
scenario are very likely more severe than these
Assumptions in four aspects of the models
may affect our results: linearity between cumu-
lative carbon emissions and ocean changes, un-
certainty in projections of ecosystem drivers,
evolutionary adaptation of marine species, and
effects of ocean acidification. We show that the
first assumption is generally valid for sea sur-
face variables, but sea-bottom variables exhibit
a lag to surface warming. Thus, our projected
fisheries impacts may be more conservative (fig.
S5). Second, accuracy of the projections is con-
tingent on the outputs from the Earth system
models (6, 11). Sensitivity analyses show that proj-
ected DMCP is most sensitive to temperature
in all biomes, followed by NPP (fig. S7). At the
same time, regional comparison of present-day
ecosystem drivers with model projections shows
that global and regional-scale patterns are rel-
atively well represented for SST and surface O2,
but not well simulated for bottom O2 and NPP
(fig. S8). Specifically, NPP is largely under-
estimated in all models in the large marine
ecosystems (see supplementary materials). The
uncertainties of projections of ecosystem drivers
are particularly relevant to interpretation of our
findings for small-scale and recreational fish-
eries that operate in inshore areas where these
uncertainties are higher (7). Third, in DBEM,
species’ environmental preferences are based on
the assumption that their current distributions
are in equilibrium with the environment and
species’ traits do not evolve as environmental
conditions change. Experimental studies suggest
that there may be standing genetic variability
that would allow species to adapt evolutionarily
to warming, while transgenerational adaptations
may also be possible for a few studied species
(27). Species distribution models that assume
adaptation potential for species’ thermal toler-
ance project lower species local extinction, par-
ticularly in the tropics (18). However, the extent
of such adaptation responses is unclear, as em-
pirical analysis of species turnover in the tropics
is currently understudied. Moreover, climate im-
pacts on habitats such as coral reefs and estuaries
may further increase the impacts on the associ-
ated species. Last, this study does not consider
the effects of ocean acidification and potential
interactions with other human drivers such as
pollution or socioeconomic development on ma-
rine fisheries. Empirical evidence suggests that
exploited mollusks and echinoderms are sensitive
to ocean acidification. Although the direct effects
of ocean acidification on finfishes in general are
inconclusive (28), indirect impacts on primary
and secondary production, behavior, and trophic
interactions may negatively affect finfish produc-
tivity (29). Thus, the addition of ocean acidification
effects would further strengthen the conclusion
that reduction in CO2 emissions, which also re-
duces ocean acidification directly, reduces im-
pacts on fisheries (5).
This study highlights the clear benefits for
fisheries from achieving the Paris Agreement’s
target and fills in an important gap for the
oceans on the implications of limiting global
average temperatures to 1.5°C.
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This is a contribution of the Nippon Foundation-Nereus Program.
W. W.L.C. also acknowledges funding support from the Natural Sciences
and Engineering Research Council of Canada. Data presented in the
manuscript are available from the Dryad Digital Repository (DOI:
10.5061/dryad.pq6p2). We acknowledge the courtesy of the Integration
and Application Network, University of Maryland Center for
Environmental Science, for some images in Fig. 1.
Materials and Methods
Figs. S1 to S9
Tables S1 to S3
27 May 2016; accepted 16 November 2016
Precursor processing for plant peptide
hormone maturation by subtilisin-like
Katharina Schardon,1 Mathias Hohl,1 Lucile Graff,1 Jens Pfannstiel,2
Waltraud Schulze,3 Annick Stintzi,1 Andreas Schaller1†
Peptide hormones that regulate plant growth and development are derived from larger
precursor proteins by proteolytic processing. Our study addressed the role of subtilisin-like
proteinases (SBTs) in this process. Using tissue-specific expression of proteinase
inhibitors as a tool to overcome functional redundancy, we found that SBT activity was
required for the maturation of IDA (INFLORESCENCE DEFICIENT IN ABSCISSION), a
peptide signal for the abscission of floral organs in Arabidopsis. We identified three SBTs
that process the IDA precursor in vitro, and this processing was shown to be required for
the formation of mIDA (the mature and bioactive form of IDA) as the endogenous signaling
peptide in vivo. Hence, SBTs act as prohormone convertases in plants, and several
functionally redundant SBTs contribute to signal biogenesis.
Small posttranslationally modified peptides function as extracellular signaling molecules in plants (1). Such peptides control plant growth and development, as well as inter- actions between plants and their environ-
ment (1, 2). Addressing the biogenesis of plant
peptide hormones, we focused on a peptide that
serves as a signal for the abscission of floral organs
(petals, sepals, and stamens).
Abscission is on full display during autumn,
when deciduous trees shed their leaves. The abscission process is also agriculturally important,
as it facilitates the dispersal of fruits and seeds.
In most flowering plants, including Arabidopsis
1594 23 DECEMBER 2016 • VOL 354 ISSUE 6319 sciencemag.org SCIENCE
RESEARCH | REPORTS