by Natalie Parletta
A huge Ginkgo tree in Strasbourg, France.
Alexander Sorokopud / Getty Images
they can defy
Some large trees have steadfastly endured for hundreds, even
thousands of years, surviving through generations of humans and
other plants and animals - but how they do this has been a mystery.
Researchers have now shown that
Ginkgo biloba trees, some of the
oldest on Earth, don't enter
senescence, the declining division
and growth of cells that inevitably results in aging and death, and
retain strong resistance to external stressors.
"Ginkgo biloba is a
living fossil, which originated about 280 million years ago,"
says first author Li Wang from Yangzhou University in China.
With no living relatives
in the division
Ginkgophyta, it has survived
glaciations and lived alongside dinosaurs.
It grows widely at different latitudes and elevations, with many of
the current specimens distributed in China, Japan and Korea, among
In China, especially,
"hundreds of G.
biloba trees aged over 1000 years still grow well and
luxuriantly and produce large numbers of seeds," says senior
author Jinxing Lin from the Beijing Forestry University.
"This phenomenon is of great interest to us. How long can these
old Ginkgo trees live?"
To explore how they
survive so long, the team conducted RNA sequencing of the vascular
cambium - the main growth tissue in the stem that produces inner
wood cells and outer bark cells - in 15- to 667-year-old Ginkgo
Most previous research on the aging of trees investigated the
leaves, which is inappropriate with Ginkgo, a deciduous tree that
loses its leaves each year.
vascular cambium," says Wang,
"which can better reflect the aging processes since it is
indeterminate and continues to function throughout the lifespan
of the tree."
They expected that
600-year-old trees would show signs of senescence, along with marked
differences to their 20-year-old juniors.
But, although several genes related to cell division, expansion and
differentiation showed reduced expression in the old trees, there
was no significant increase in the expression of genes related to
The old trees also had similar leaf areas, efficiency of leaf
photosynthesis and seed germination rates to their younger
counterparts and retained high expression of genes associated with
disease resistance and synthesis of protective metabolites.
"It seems that the
vascular cambium in G. biloba retains the capacity for
continuous growth for hundreds of years or even millennia, and
this may enable G. biloba to escape senescence at the whole
plant level in the absence of outside accidents," says Lin.
"On top of this, the remarkable maintenance of expression of
genes associated with biotic stress was unexpected. In humans,
for example, our immune systems gradually become compromised
The team expects that
most ancient trees are likely to have this longevity mechanism
whereby the continuous division of the vascular cambium can
compensate for the aging process, similarly to cancer or germ cells
So, if the trees don't enter senescence, how do they die?
"This is a difficult
question," says Wang.
Most trees die from
diseases, pests and other environmental stressors such as extreme
weather or bush fires.
These causes aside, plants and animals have dramatically different
developmental patterns, explains co-senior author Richard Dixon
from the University of North Texas, US, especially in their
In most animals,
organs and tissues show little difference over the lifespan,
apart from growth, maturation and eventually senescence and
Plants, on the other
hand, constantly form new organs and tissues, which might help
them avoid the whole-plant senescence process.
Senescence might still occur with trees older than 1000 years, a
possibility that can't be ruled out with the current study,
More information should
come to light with new methods for analyzing an organism's entire
genome, as used in the present study, which have only recently
It should be noted that the research, not easy to do with old trees
because they grow slowly and their lifespans dwarf ours, is a
"static snapshot" of the tree's status at the time of harvest, says
Dixon, noting that it would be more challenging to work out how
different ages respond to stress in real time.
The paper (Multifeature
analyses of vascular cambial cells reveal longevity mechanisms in
old Ginkgo biloba trees) is published in the journal
Proceedings of the National Academy of Sciences.