Carotenoid Biosynthesis in Reproductive Organs of Wild-Type and a Pale Anther Mutant of Diploid Strawberry Fragaria vesca

Carotenoids are lipophilic tetraterpenoid pigments found in most plant organs.  In leaves, carotenoids serve as light harvesting complexes, and are responsible for protection against reactive oxygen species generated in the chloroplast.  Carotenoids are also precursors for the production of signaling compounds such as abscisic acid and strigalactone.  In flowers and fruits, carotenoids act as visual attractants for pollinators and seed dispersers, and may serve as protective antioxidants in these organs.

Flowers of F. vesca have yellow-orange anthers, yellow carpels, and yellow pollen due to the presence of carotenoids, but the precise roles of these pigments have not been defined.  We are assessing the potential for these compounds to protect reproductive organs against abiotic stress using biochemical analysis, genomics, and genetics. An EMS induced mutant called pale male (pml), which has pale yellow/white anthers, produces no pollen, and completely retains petals after the flower has opened independent of fertilization status, is being studied as part of this work.

Candidate genes involved in carotenoid biosynthesis were identified, revealing the existence of small gene families.  Gene expression patterns throughout the plant, and expression in wild-type (wt) in response to moderate heat stress and in the mutant were analyzed by QRTPCR.  Mass spectrometric analyses of carotenoids in control and heat stressed tissues and in pml showed decreased accumulation of lutein in leaves and increased lutein and α-cryptoxanthin in anthers of wt in response to heat, and strikingly increased α-cryptoxanthin accumulation in anthers of the mutant as compared to wild-type at normal temperatures.