Stress Response of Reproductive Pathways in Facultative Apomictic Ranunculus Auricomus Hybrids

Almost all modes of asexuality in eukaryotes maintain meiosis and residual sexuality either in a modified form or as an alternative pathway. In flowering plants, apomixis, the asexual reproduction via seed, is usually facultative, which means that both sexual and asexual offspring can arise from the same mother plant within the same offspring generation. Frequencies of facultative sexuality appear to vary according to environmental conditions. We hypothesize that differential response to environmentally induced, intracellular oxidative stress influences expression of meiosis and consequently facultative sexuality (Hörandl & Hadacek 2013, Plant Reproduction 26: 351–367). Here we present experimental work on hexaploid clone-mates of Ranunculus auricomus to test the hypothesis that (1) progeny of apomictic, self-pollinated mother plants cultivated under equal conditions exhibits genotypic variation resulting from facultative recombination; (2) clone-mates produce higher frequencies of sexual offspring under light stress; (3) plants increase under stress conditions their expression of ROS-scavenging secondary metabolites, and (4) expression of sexuality under stress conditions might be genotype-specific. Plants produced in progeny arrays were genotyped with six microsatellite markers developed from an RNAseq dataset, and treated in climate growth chambers under different photoperiods. We screen for frequencies of aposporous initials vs. functional megaspores via DIC microscopy, and for sexual vs. apomictic seed formation via flow cytometric seed screening. Phenolic metabolites in flowering buds are being screened via HPLC-DAD. Results will be discussed with respect to evolutionary consequences and inference for understanding genetic control mechanisms of apomixis.