SEMINAR: Plant Biology Research Seminar

For annual plants, the seasonal timings of seed germination and of flowering are important life cycle events with significant implications for ecological adaptation and fitness. Synchronized germination and reproduction are also critical for efficient production of annual crops. We have used natural variation and QTL mapping to identify genes associated with the regulation of lettuce (Lactuca sativa) seed germination in response to temperature. Genes involved in both abscisic acid biosynthesis and ethylene action have been mapped and confirmed as being involved in thermoinhibition of lettuce seed germination. Additional QTL have been identified associated with maternal environment effects (i.e., GxE interactions) on seed dormancy. A homolog of a gene known to regulate maternal effects on seed dormancy in Arabidopsis (DOG1) was confirmed in lettuce and surprisingly, manipulation of its expression resulted in effects on flowering time. Further work in lettuce and Arabidopsis indicates that this is due to modification of microRNA levels (specifically miR156 and miR172) that have dual action on both seed dormancy and flowering. A common molecular mechanism for the environmental specification of both germination and flowering life cycle transitions may underlie the coevolution of these traits in natural populations.