SUPRA-OPTIMAL TEMPERATURE CAUSES ROS ACCUMULATION AND REDUCES SEED FAILURE IN SOYBEANS

The goal of this project is to investigate the physiological mechanisms by which elevated temperature limits reproductive fertility, seed growth, and yield. Models of global climate change reveal that many farmers will be growing crops under warmer environmental conditions (+1 to 6 C). In seed-producing crops, this will result in fewer, smaller seeds and reduced harvests. Temperature stress induces reactive oxygen species (ROS) accumulation in developing ovules and seeds. In soybeans and Arabidopsis, the fraction of ovules that accumulate high levels of ROS equals the fraction of ovules that abort, leading to the hypothesis that this causes ovule and seed abortion. Experiments will be done to determine if an increase in ROS scavenging activity in developing soybean seeds increases soybean yield and seed vigor. These seeds will also be evaluated to see if they have reduced levels of lipid peroxides, which give oils a rancid flavor. An alternative explanation for this ROS accumulation is that reduced O2 availability in seeds could result in alternative electron acceptors being used. Research shows that the soybean seed coat limits O2 diffusion, reducing seed growth, development, and yields. Temperature and O2 treatments will be imposed during floral bud and seed development to determine if reproductive failures (pollination and seed growth) under elevated temperature are mediated by limiting O2 levels. Different temperature treatments will cause differential pO2 inside seed, which can be correlated with energy status, ROS level, metabolite levels, and success in seed growth. Many important seed-producing species show similar patterns of reproductive growth in response to supra-optimal temperatures so findings from this research will be applicable to other species.