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able the identification of proxy measures for

larger-scale assessments and biogeochemical

models. For instance, Werner et al. found

characteristic blends of volatiles released

by drought-stressed vegetation that can

function as indicators of different levels of

drought stress and plant senescence. Such in-

formation is urgently needed to improve the

predictive capacity of biogeochemical models

( 1 , 12 ). At the same time, following carbon

and water dynamics with targeted labeling

experiments was mostly possible above the

ground, whereas continuously measuring

labels in belowground organs, such as fine

roots, still poses major challenges that need

to be addressed in future work. New facilities

like the Deep Soil Ecotron ( 13 ) will help elu-

cidate belowground processes, going beyond

the topsoil and down to a depth of 3 m.

The results by Werner et al. indicate that

climate extremes like drought can modulate

the balance between carbon sink and source

processes through changes in plant physi-

ology, plant carbon allocation, and plant-

soil-atmosphere interactions. Such insights

are critical for linking local experimental

studies and global monitoring and model-

ing approaches. Data availability and infor-

mation gained from global networks such

as FLUXNET ( 14 ), which measures surface

gas exchange between terrestrial ecosystems

and the atmosphere, or remote sensing ( 15 )

across major terrestrial biomes are continu-

ously improving and will allow the assess-

ment of changes in biodiversity, ecosystem

functioning, and stress levels based on proxy

variables provided by local experimental

work. Given that evapotranspiration, ecosys-

tem respiration, and gross primary produc-

tivity all responded substantially to drought

in the Biosphere 2 study, future projects

should explore whether the plant traits iden-

tified as related to drought resistance have

similar predictive power across ecosystem

types and biomes. Integrating information

on plant functional types related to drought

resistance and resilience with the role of

soils in water and carbon dynamics will help

develop a predictive framework for ecosys-

tem effects of extreme events and help pa-

rametrize Earth system models by account-

ing for coupled plant-soil interactions. j

REFERENCES AND NOTES

1. H. O. Pörtner et al., IPBES-IPCC co-sponsored workshop
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2. G. B. Bonan, Science 320 , 1444 (2008).


3. C. Werner et al., Science 374 , 1514 (2021).


4. L. S. Leigh, T. Burgess, B. D. V. Marino, Y. D. Wei, Ecol. Eng.
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5. W. R. L. Anderegg, A. T. Trugman, D. R. Bowling, G.
   Salvucci, S. E. Tuttle, Proc. Natl. Acad. Sci. U.S.A. 116 ,
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6. F. Schnabel et al., bioRxiv 10.1101/2021.01.06.425434
   (2021).


7. F. J. Bongers et al., Nat. Ecol. Evol. 5 , 1594 (2021).


8. A. Weigelt et al., New Phytol. 232 , 42 (2021).


9. F. I. Pugnaire et al., S c i. A d v. 5 , eaaz1834 (2019).


10. U. Pöschl et al., Science 329 , 1513 (2010).


11. A. Canarini et al., Nat. Commun. 12 , 5308 (2021).


12. J. Roy et al., Glob. Change Biol. 27 , 1387 (2021).


13. E. Stokstad, Science 373 , 250 (2021).


14. M. Migliavacca et al., Nature 598 , 468 (2021).


15. A. K. Skidmore et al., Nat. Ecol. Evol. 5 , 896 (2021).

ACKNOWLEDGMENTS

We acknowledge the support of iDiv funded by the German

Research Foundation (DFG) (DFG–FZT 118, 202548816).

The Jena Experiment is funded by the DFG (FOR 5000). We

appreciate helpful comments by C. Werner.

10.1126/science.abn1406

Total canopy water flux

Soil water levels:

Predrought Severe drought Recovery

Gross primary productivity

27%

32%

63%

90%

100%

Drought-sensitive species Drought-tolerant species Volatiles

100%

High Low

By F ilip Bošković and Ulrich F. Keyser

M

ost sequencing methods for nu-

cleic acids require multiple cop-

ies of the target molecules. The

copying of nucleic acids, through

polymerase chain reaction (PCR),

enabled next-generation sequenc-

ing technology that uses more finite tar-

gets. This has allowed the development of

genomics and transcriptomics approaches

to profile single cells. Proteins are argu-

ably more important for the proper func-

tion of living systems, and so proteomics

methods that provide the identity, quantity,

and sequence of proteins in a single cell is

a key goal. However, one obstacle in pro-

tein sequencing is our inability to make

identical copies of proteins. On page 1509

of this issue, Brinkerhoff et al. ( 1 ) develop a

method to reread a single polypeptide many

times, which allows the identification of

synthetic peptide variants. Their approach

is based on nanopore DNA sequencing and

overcomes one of the biggest obstacles to-

ward single-molecule proteomics.

Protein sequencing currently relies on

mass spectrometry–based methods that re-

quire large amounts of starting materials

and miss rare proteins. The quantification

of messenger RNA molecules generally does

not reflect the proteome ( 2 ). Hence, for an

accurate determination of cellular protein

isoforms and variants, including their post-

translational modifications (PTMs), new

methods are needed. Often inspired by DNA

sequencing approaches, several methods

have been proposed, including single-mol-

ecule fluorescence, tunneling current analy-

sis, and nanopore sequencing ( 3 ). Nanopore

DNA sequencing involves ionic current

sensing for the identification of single nu-

cleotides in nanopores ( 4 ). This inspired

Cavendish Laboratory, University of Cambridge,

Cambridge, UK. Email: [email protected]

MOLECULAR BIOLOGY

Toward single-

molecule

proteomics

Nanopore rereading of

single proteins opens a

pathway to next-generation

proteomics

INSIGHTS

Tropical forest responses to drought and rewetting

In Biosphere 2, drought effects revealed major changes to water and carbon fluxes, volatile compound

composition by vegetation and uptake by soil, and gross primary productivity in a tropical forest ecosystem.

After rewetting, water and carbon fluxes slowly recovered, but not to predrought levels.

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