Calcium regulation within dormant
potato tuber buds
Cláudia Carvalho
Dr Richard Colgan
Dr Debbie Rees
Why calcium is important to tubers?
 Calcium (Ca2+) is essential in growth and development in plants and has
important roles in:
• cell division
• membrane integrity and function
• as secondary messenger in various metabolic processes
 Ca2+ increases membrane integrity
Low concentrations of Ca2+ in cell membranes
Anti-senescence factor
Membrane leakage
Cell death
Ca2+ supply to the tuber
 Ca2+ moves in the plant through xylem
 Tuber Ca2+ content can be increased by
placing Ca2+ near stolon areas of the tuber
Functional roots on the tuber
and at the tuber-stolon junction
http://www.yara.com.au/crop-nutrition/crops/potato/key-facts/role-of-calcium/
Water and Ca2+ to the tuber
Calcium role in sprout growth in potato
 Early works reported the effect of Ca2+ on tuber sprouting
 Cells can access to Ca2+ in two ways
• finite stores located in the ER and vacuoles
• extracellular Ca2+
implications on the
sprouting potential of tubers
Ca2+ homeostasis maintenance
 The most potent factor in shaping
[Ca2+]cyt signatures is the activity of Ca2+
efflux systems
 There are two groups of Ca2+ efflux
mechanisms:
•
Ca2+ -
ATPases
involved in
termination of
[Ca2+]cyt signaling (?)
high-affinity, low-capacity transporters
• Ca2+ exchangers
(CAX)
involved in removal
of [Ca2+]cyt when
[Ca2+]cyt elevations
are higher than
normal (?)
low-affinity, high-capacity transporters
Bose et al., 2011
Calcium role in dormancy break
 Ca2+ availability was linked with dormancy break in plants:
• In grapes the inactivation of Ca2+
extended dormancy in grape buds
 Ca2+ role efflux systems in shaping up [Ca2+]cyt signatures
It is believed that each [Ca2+]cyt
signatures due to a developmental
signal or environmental factor is
unique
An increasing in [Ca2+]cyt is affected by
Ca2+ influx to the cytosol
Bose et al., 2011
Aims and objectives
 Test the effect of Ca2+ and plasma membrane calcium channel blocker
LaCl3 and the calcium chelator EGTA on dormancy break and sprout
vigour on excised potato tuber buds.
 Determining the amount of calcium chloride (CaCl2), LaCl3 and EGTA
required to influence bud break and sprout growth
Aims and objectives
 Effect of such treatments on apical and lateral buds selected from the
middle and stolen end spatial distribution, to disentangle the influence of
apical dominance on dormancy break found in whole tubers.
Apical
Stolon
Middle
Ca2+ bioassay
Middle
Apical
Incubate in dark at 20oC
Stolon
Shoot length (mm): Apical
 Buds incubated in Ca2+ produced more
rapid shoot growth than the buds
incubated in deionized water (0 mM)
 Buds treated with EGTA and LaCl3 had a
slower rate of bud emergence and
sprout growth
Shoot length (mm): Middle
 Buds incubated in Ca2+ produced more
rapid shoot growth than the buds
incubated in deionized water (0 mM)
 Buds treated with EGTA and LaCl3 had a
slower rate of bud emergence and
sprout growth
Shoot length (mm): Stolon
 Buds incubated in Ca2+ produced more
rapid shoot growth than the buds
incubated in deionized water (0 mM)
 Buds treated with EGTA and LaCl3 had a
slower rate of bud emergence and
sprout growth
Dormancy prediction
Effect of calcium blockers on bud dormancy of
two different varieties (apical + stolen buds)
d
A Weibull distribution
cd
bc
cd
analysis was used to
estimate the number of
days each treatment
a
a
a
a
a
a
a
a
extended dormancy
Buds treated with EGTA or LaCl3 remained dormant for longer than the
ones treated with Ca2+ or untreated (0 mM)
Means with the same letter are not significantly different according to Tukey test (p < 0.05)
Conclusions
 Reducing Ca2+ availability delays bud sprout and shoot
growth
 The effectiveness of Ca2+ and EGTA was influence by
location of the bud on the tuber
 LaCl3 was as effective irrespective of bud location
 Ca2+ important for the initiation of dormancy break and
shoot growth
Acknowledgements
Dr. Richard Colgan
Dr. Debbie Rees
Dr. Stephen Young
Thank you for listening…
Questions?
email: [email protected]