Carotenoids are tetraterpenoid lipophilic pigments found in most plant organs. In leaves, carotenoids serve as light harvesting complexes, and they 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, the colors of carotenoids play roles as visual attractants for pollinators and seed dispersers, and roles as antioxidants in these organs are also probable. Strawberry production depends on successful development of reproductive structures and fertilization, processes highly susceptible to abiotic stresses. Insight into the functions of carotenoids in reproductive organs could provide the groundwork for breeding or genetically engineering more stress tolerant strawberries and other horticultural crops. Flowers of the diploid woodland strawberry, F. vesca, have yellow-orange anthers, yellow carpels, and yellow pollen due to the presence of carotenoids, but the precise role(s) of these pigments have not been defined. We are assessing the potential for these compounds to protect reproductive organs against elevated temperature stress using biochemical analysis, genomics, and genetics. Unlike in leaves, HPLC analysis showed that developing F. vesca carpels and stamens have no detectable beta-carotene. Candidate genes involved in carotenoid biosynthesis were identified, revealing the existence of small gene families. Gene expression patterns throughout the plant, and expression in response to heat stress in the reproductive structures were analyzed by QRTPCR. Mass spectrometric analyses of carotenoids in control and heat stressed tissues, and in a male sterile mutant with pale anthers are underway.
