Oleh Irda Safni
Senescence
dan
Autumnal senescence
Pathogen-induced
cell death
Nutritional senescence
Reproductive senescence
Developmental
cell death
Photos courtesy Tom Donald; IRRI ; Gunawardena, A.H.L.A.N., Greenwood, J.S. and Dengler, N.G. (2004). Programmed cell death remodels lace plant leaf shape during development. Plant Cell. 16: 60-73; Park, S.-Y., et al. (2007). The senescence-induced Staygreen protein regulates chlorophyll degradation. Plant Cell. 19: 1649-1664
Senescence is a slow process of nutrient
reassimilation followed by death
Senescence:
•is an
active
developmental
program that requires
upregulation of many genes
• is
not
simply necrosis or
death by neglect
Senescence is a process by which nutrients
are remobilized into seeds (annual plants) or
bark and other tissues of long-lived plants
Programmed cell death (PCD)
Image credits: "Illustrated Information". Nobelprize.org. 31 Oct 2011
Programmed cell death is a
normal developmental
program that removes cells
from between the digits and
inside the intestinal lumen
Programmed cell death (PCD) is an active process to
remove unneeded or damaged cells. Breakthroughs in our
understanding came from studies of
C. elegans
, culminating
Examples of plant PCD
Death during defense
Death during development
PCD is a developmental program
in many tissues
Leaf
Organ abortion in
unisexual flowers
Hole development
in lace plant leaf
Extra
embryos
Suspensor
Adapted from Gadjev, I., Stone, J.M., and Gechev, T.S. (2008) Programmed cell death in plants: new insights into redox regulation and the role of hydrogen peroxide. Int. Rev. Cell Mol, Biol. 270: 87 – 144. ; Reprinted by permission from Macmillan Publishers Ltd Filonova, L.H., von Arnold, S., Daniel G., and Bozhkov, P. V. (2002) Programmed cell death eliminates all but one embryo in a polyembryonic plant seed.
Cell Death and Differen. 9: 1057-1062.Bennett, T., et al. (2010). SOMBRERO, BEARSKIN1, and BEARSKIN2 Regulate Root Cap Maturation in Arabidopsis. Plant Cell. 22: 640-654.
Tracheary element formation in
Zinnia
elegans
cells is a model for PCD
Lacayo, C.I., Malkin, A.J., Holman, H.-Y.N., Chen, L., Ding, S.-Y., Hwang, M.S. and Thelen, M.P. (2010). Imaging cell wall architecture in single Zinnia elegans tracheary elements. Plant Physiology. 154: 121-133; Adapted from Turner, S., Gallois, P. and Brown, D. (2007). Tracheary element differentiation. Annu. Rev. Plant Biol. 58: 407-433.
Mesophyll cell
Tracheary element
Isolated mesophyll cells can form
tracheary elements in culture, allowing
identification of genes involved in PCD
Defensive cell death
Reprinted by permission from Macmillan Publishers Ltd Lam, E. (2004) Controlled cell death, plant survival and development. Nat. Rev. Mol. Cell Biol. 5: 305 – 315. Image credit: Nicolle Rager Fuller, National Science Foundation
The
hypersensitive response
Developmental
signals
Environmental
signals
Disassembly of
cellular contents and
degradation of
macromolecules
Cell death
Decrease in
photosynthesis,
activation of
senescence program
Developmental senescence
In
monocarpic
plants, reproduction triggers senescence.
Monocarpic plants flower once, set seed and die.
Most crop plants are monocarpic
Photoperiod induces leaf
senescence in autumn leaves
Bhalerao, R., Keskitalo, J., Sterky, F., Erlandsson, R., Björkbacka, H., Birve, S.J., Karlsson, J., Gardeström, P., Gustafsson, P., Lundeberg, J., and Jansson, S. (2003). Gene expression in autumn leaves. Plant Physiology 131: 430-442; Keskitalo, J., Bergquist, G., Gardeström, P. and Jansson, S. (2005). A cellular timetable of autumn senescence. Plant Physiol. 139:
1635-1648.
Day length
is the signal that
initiates
leaf senescence, but the
rate
at which senescence occurs
is affected by
temperature
Autumn
Drought and other stresses induce
leaf senescence
Reprinted with permission from Buchanan-Wollaston, V., Page, T., Harrison, E., Breeze, E., Lim, P.O., Nam, H.G., Lin, J.-F., Wu, S.-H., Swidzinski, J., Ishizaki, K. and Leaver, C.J. (2005). Comparative transcriptome analysis reveals significant differences in gene expression and signalling pathways between developmental and dark/starvation-induced senescence in Arabidopsis. Plant J. 42: 567-585.
Reproduction
Metabolism
Stress
Hormones may contribute differently
to different types of senescence
The onset of senescence brings about a
change in gene expression
From Buchanan-Wollaston, V. (1997). The molecular biology of leaf senescence. Journal of Experimental Botany. 48: 181-199 as adapted in Buchanan, B.B., Gruissem, W. and Jones, R.L. (2000) Biochemistry and Molecular Biology of Plants. American Society of Plant Physiologists.
Expansion
Maturity
senescence
Visible
Necrosis
Breeze, E., et al., and Buchanan-Wollaston, V. (2011). High-resolution temporal profiling of transcripts during Arabidopsis leaf senescence reveals a distinct chronology of processes and regulation. Plant Cell 23: 873-894.
Days after
sowing
Proteins
Chlorophyll degrades during
senescence
Woo, H.R., Chung, K.M., Park, J.-H., Oh, S.A., Ahn, T., Hong, S.H., Jang, S.K. and Nam, H.G. (2001). ORE9, an F-Box protein that regulates leaf senescence in Arabidopsis. Plant Cell. 13: 1779-1790.
The first visible sign of leaf senescence is chlorophyll breakdown
In some plants this is
accompanied by
unmasking of
carotenoids
or
accumulation of
anthocyanins
, turning
Carotenoids and anthocyanins absorb
and dissipate excess light energy
Pre-senescent:
Light is absorbed and
drives photosynthesis
- Chl
- Chl
+ anthocyanin
Anthocyanin
Mechanisms of senescence -
summary
Leaf senescence has many
triggers
Different hormones are
involved in different types of
senescence, and different
sets of genes are induced
Economic impacts of senescen
ce
Reprinted from Peleg, Z, and Blumwald, E. (2011) Hormone balance and abiotic stress tolerance in crop plants. Curr. Opin. Plant Biol. 14: 290–295 with permission from Elsevier.
Wild type -
Well Watered
Wild type -
Drought Stressed
Senescence-induced
cytokinin synthesis -
Drought Stressed
Delaying
senescence
can enhance
drought
Timing of senescence affects yield
and grain quality
From Uauy, C., Distelfeld, A., Fahima, T., Blechl, A. and Dubcovsky, J. (2006). A NAC gene regulating senescence improves grain protein, zinc, and iron content in wheat. Science. 314: 1298-1301. Reprinted with permission from AAAS.
Delayed senescence
Delaying senescence
increases total
photosynthesis and can
increase grain yields
However, delaying senescence
can also reduce mobilization of
nutrients into the seeds,
Senescence affect post-harvest
food quality
Broccoli – day of harvest
Broccoli – five days post- harvest
How can food-shelf-life be enhanced?
•Cold temperatures
•Low oxygen-environment
•Ethylene removal or ethylene insensitivity
•Increased cytokinin synthesis or responsiveness
•Other genetic methods to delay senescence
Harvesting can
induce senescence,
particularly in broccoli
and asparagus
Petal senescence affects a $100
billion industry
How much more would you pay for
roses guaranteed to stay pretty for
two or more weeks?
Petal senescence in
Ipomoea nil
(morning glory
)
Yamada, T., Ichimura, K., Kanekatsu, M. and van Doorn, W.G. (2009). Homologs of genes associated with programmed cell death in animal cells are differentially expressed during senescence of Ipomoea nil petals. Plant Cell Physiol. 50: 610-625; Yamada, T., Ichimura, K. and van Doorn, W.G. (2006). DNA degradation and nuclear degeneration during programmed cell death in petals of Antirrhinum, Argyranthemum, and Petunia. J. Exp. Bot. 57: 3543-3552 with permission from Oxford University Press.
The
biochemistry of
senescence in
petals is similar
Death and Senescence - Summary
Death matters:
From embryogenesis to
senescence,
programmed cell death
is essential for plant
fitness and viability
Understanding death and
senescence is important:
As we learn more about
these processes we
decrease food losses to
stress and disease, and
enhance yields and quality of
Senescence and Plant Disease
Many plant pathogens show interactions with host
development.
Pathogens may modify plant development according to their
nutritional demands.
Conversely, plant development influences pathogen growth.
Biotrophic pathogens often delay senescence to keep host
cells alive, and resistance is achieved by senescence-like
processes in the host.
Necrotrophic pathogens promote senescence in the host,
and preventing early senescence is a resistance strategy of
plants.
On the one hand, developmental conditions of the host plant
may determine the outcome of pathogen infection.
On the other hand, pathogen infection can change the
developmental program of the host.
Symptoms of senescence often accompany the progression
of disease.
In other cases, senescence is delayed in response to
pathogen infection.
Payers in the control of senescence and pathogen defense:
Hormon tumbuhan, seperti:
a. Etilen
b. Asam Jasmonik
c. Asam Salisilat
d. Asam Absisat
e. Brassinosteroids (BR) sebagai hormon yang mempromosikan
senescence
Merupakan pemain penting dalam mengendalikan senescence dan
pertahanan patogen.
Hormon tanaman,seperti:
a.Sitokinin
b.Auksin
c.Gibberellin
Hormon Etilen
Berperan berlawanan pada interaksi dengan patogen
necrotropik dan hemibiotropik, yaitu:
1.Etilen terutama mempromosikan senescence
2.Etilen juga berperan pada program kematian sel.
Penuaan dan kematian sel bermanfaat bagi patogen
nekrotropik.
Sehingga mensintesa etilen adalah strategi virulensi yang
digunakan patogen nekrotropik dan hemibiotropik.
Akan tetapi, Etilen berinteraksi secara bersinergi dengan
Hormon Etilen
Hormon Asam Jasmonik
Asam Jasmonik memegang peranan penting dalam
pengendalian senescence, kematian sel dan ketahanan
terhadap patogen nekrotropik.
Asam Jasmonik dan Asam Absisat membantu ketahanan
Hormon Asam Salisilat
Asam Salisilat terutama dikenal sebagai hormon
pertahanan, tetapi juga memeiliki peran ganda di dalam
mempromosikan perkembangan senescence.
Asam Salisilat juga dibutuhkan
Hypersensitive Response,
pada saay terjadinya kematian sel secara lokal. Selama
Hormon Asam Absisat (ABA)
ABA mungkin yang paling berperan ganda dalam regulasi
senescence dan dalam pengendalian ketahanan terhadap
patogen.
Di satu sisi, ABA termasuk hormon yag memperomosikan
senescence.
Di sisi yang lain, ABA sangat berperan pada ketahanan
Figure 7.
A model for the roles of potentially senescence-inducing signaling molecules during necrotrophic
host-pathogen-interactions. Ethylene (ET), jasmonic acid (JA), salicylic acid (SA), abscisic acid (ABA) and reactive oxygen
species (ROS) are usually induced during necrotrophic interactions. If the senescence-promoting effects prevail, host
susceptibility will be increased. If the host succeeds to restrict signaling events to defence-related branches, resistance can
be achieved. Regulatory nodes, such as transcription factors, may act as molecular switches between signaling branches.
Colored arrows symbolize signaling pathways triggered by different signaling molecules. Dashed arrows symbolize
potential responses. PTI = PAMP-triggered immunity, SAR = systemic acquired resistance, PAMP =
pathogen-associated molecular pattern.
ET
Suppression of JA/ET- defences
Suppression of JA/ET- defences
Cell death and necrosis
Defence against necrotrophs
