WINEFIELD, CHRISTOPHER S1*, KEVIN S GOULD2, and KENNITH R MARKHAM3. 1New Zealand Institute for Crop and Food Research Ltd, Private Bag 11600, Palmerston North, New Zealand; 2School of Biological Sciences, University of Auckland, P.O. Box 92019, Auckland New Zealand; 3Industrial Research Ltd, P.O. Box 31310, Lower Hutt, New Zealand. - Flavonoid sequestration within the vacuolar compartment: A potential role for protein:anthocyanin interactions.
In a wide range of species, floral pigmentation is due to the
accumulation of anthocyanin pigments in the vacuoles of the flower
epidermis. In most cases the accumulating anthocyanins are found
evenly distributed throughout the vacuolar solution. However in a
number of plants there have been reports of aggregations of
anthocyanins within the vacuole. These aggregations have been
variously described as "blue spherules" in epidermal cells
of rose petal, "intravacuolar spherical bodies" in
Polygonum cuspidatum seedlings, "ball-like
structures" and "crystals" in stock Matthiola
incana, petals, "blue crystals" in Larkspur,
Consolida ambigua, and red "crystals" in mung bean
hypocotyls. We have recently identified and begun characterisation of
similar entities in Eustoma grandiflorum (lisianthus) and
Dianthus caryophyllus (carnation). We have termed these
structures Anthocyanic Vacuolar Inclusions or AVIs. They are
non-membrane bound aggregations of highly pigmented material found in
the vacuoles of the petal epidermis. The presence of these structures
results in intensification in colour and a significant shift in the
absorbance spectra of anthocyanins in these cells. We have isolated
the AVIs from the inner region of lisianthus petals and have
identified that they consist of a protein:anthocyanin complex to which
only a subset of the anthocyanins and flavonoids produced in these
tissues is bound. The ongoing characterisation of this complex and the
potential implications of these interactions on flavonoid
sequestration in plant tissues will be discussed.
Key words: Anthocyanic Vacuolar Inclusions, Eustoma grandiflorium, protein, trap