Science 14Feb2020

PHOTO: NIGEL CATTLIN/MINDEN PICTURES

sciencemag.org SCIENCE

new information, researchers

can construct a more complete

picture of the predation, diet,

geography, and ecology of this

species. —DHE

Sci. Adv. 10.1126/sciadv. aay4593

(2020).

PHYSICS

Understanding

fragile topology

Exploiting topological features

in materials is being pursued as

a route to build in robustness of

particular properties. Stemming

from crystalline symmetries,

GERM CELL BIOLOGY

Conserved gene

specifies germ cell

Germ cells are the exclusive

progenitors of gametes. In

most studied animals, includ-

ing humans, germ cells are

produced only once during

embryogenesis and are not

replenished in adult life. DuBuc

et al. studied germ cell induc-

tion in the clonal cnidarian

Hydractinia symbiolongicarpus,

an animal that forms germ

cells continuously in adult

life from stem cells that also

generate somatic cells. A single

transcription factor is capable

of converting the animal’s adult

stem cells to germ cells. A

similar gene also controls germ

cell induction in mammalian

embryos, but its action there is

limited to a single event in early

embryogenesis. —BAP

Science, this issue p. 757

PALEONTOLOGY

More evidence for

a massive turtle

Partial specimens of the extinct,

nonmarine turtle Stupendemys

geographicus have given

paleontologists some indica-

tion of its truly massive size,

but the biology and systemat-

ics of this species remained

unclear. Cadena et al. found

remains in La Tatacoa Desert in

Colombia that set a size record

for the largest known complete

turtle shell—2.40 meters from

neck to tail—and represent

the first lower-jaw specimens

from the Urumaco region since

1994. These data support the
      interpretation that there was
      only one giant erymnochelyin
      taxon that exhibited sexual
      dimorphism, with horns in males
      and hornless females. With this

PLANT PATHOLOGY

A plant pan-genome

immunity landscape

P

lant pathogens elicit an immune

response through effector

proteins. In turn, plant genomes

encode genes that determine

species-specific recognition of

these effectors by a process known

collectively as effector-triggered immu-

nity (ETI). By examining a range of

strains of the pathogen Pseudomonas

syringae that infect the model plant

Arabidopsis thaliana, Laflamme et al.

generated a P. s y r i n g a e Type III Effector

Compendium (PsyTEC) and in turn

identified the genes responsible for

ETI in Arabidopsis. This pan-genome

analysis revealed that relatively few

A. thaliana genes are responsible for

recognizing the majority of P. syringae

effectors. These results provide insight

into why most pathogenic microbes

only infect specific plant species. —LMZ

Science, this issue p. 763

IN SCIENCE JOURNALS

English laurel afflicted by the bacterial plant

pathogen Pseudomonas syringae, subspecies

of which cause various diseases in plants.

Edited by Michael Funk

RESEARCH

752 14 FEBRUARY 2020 • VOL 367 ISSUE 6479

Published by AAAS