Page 314 - PC2019 Program & Proceedings

PLANT CANADA 2019

P201. Identification and characterization of a photosynthesis-related phosphatidylinositide transfer
protein in Arabidopsis
1
1
3
Kim, E. ; H. Yu ; Y. Lee ; H. Kim ; K. Lee 1
2
1 National Institute of Agricultural Sciences
2
Pohang University of Science and Technology
Sejong University
3

We identified a phosphatidylinositide transfer protein, PITP1, localized to chloroplast in Arabidopsis.
PITP1 is crucial to plant development under both optimal and stress conditions. Three T-DNA mutants
for PITP1 were characterized: a complete knockout, pitp1-1 plant, a partial knockdown, pitp1-2 plant, and
an indistinguishable mutation from wild type, pitp1-3 plant. pitp1-1 was seedling-lethal, and pitp1-2 plant
showed smaller and pale greener than WT while pitp1-3 were not different. Essential role of pitp1 for
viability was confirmed by the complementation of pitp1-1 plant by 35S:PITP1 over expression. In
addition, phenotypes of XVE:PITP1 transgenic plant were recovered in the presence of β-estradiol. Plants
containing defective PITP1 accumulated significantly less plastoquinone-9 and its cyclized product,
plastochromanol-8, but the levels of tocopherols were not affected. pitp1-2 plant exhibited lower
photosynthetic performance under high light stress and cold stress. Accumulation of QA- was shown by
the induction of OJIP fluorescence, indicating the slow electron transfer from QA- to QB even without
DCMU. PITP1 bound to phosphatidylinositol monophosphates, phosphatidylinositol bisphosphates,
cardiolipin, and sulfatide on lipid-spotted membrane. PITP1E162K and PITP1H125Q mutation affected
the binding capacity to these lipids strongly and moderately, respectively in vitro. Expression of
PITP1E162K and PITP1H125Q in pitp1-3 plant did not fully complemented PITP1 functions. These
findings suggest that PITP1 plays important roles by binding with phosphatidylinositides in chloroplasts
for photosynthetic function, plant development, and stress responses in Arabidopsis.

Eun-Ha Kim (eunhada@korea.kr)

P202. What would you do if you had more days before shedding your leaves? Not much, said the
sink-limited plant E. americanum
*
Bertrand, H. ; L. Lapointe
Université Laval

Growth in spring ephemerals such as Erythronium americanum is modulated by sink strength rather than
source strength. Higher photosynthetic rates do not translate into higher growth rate nor higher final bulb
biomass. The excess C produced by leaves, for example under elevated CO2, is instead respired in the
bulb via the alternative respiratory pathway. However, plants growing at lower temperature appear to
maintain a better equilibrium between source and sink activity, leading to a prolonged leaf life span and a
larger bulb at the end of the growing season. We artificially prolonged leaf life span by applying Promalin
(mixture of cytokinins and gibberellins) on the leaves and examine its impact on final bulb biomass,
photosynthetic activity (gas exchange and chlorophyll a fluorescence) and respiratory rates.
Photosynthetic rates decreased through time but at a slightly slower rate in the Promalin treated plants
compared to the control. Quenching of chlorophyll fluorescence confirmed that the reduction in
photosynthetic rates was due to feed back inhibition. The prolonged leaf life of plants treated with
Promalin thus added a negligible amount of C to the bulb, as most of the C is assimilated before the
initiation of leaf senescence. These results suggest that bulb C accumulation capacity is defined during the
sink initiation phase and cannot be easily modified by prolonging leaf life span.

Hugo Bertrand (hugo.bertrand.4@ulaval.ca)

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