Genetic and Environmental Control of Lignin Biosynthesis and C Emission from Crop Stover

摘要

Lignin is the second most abundant terrestrial biopolymer in the world and provides structural strength to plants. The maize brown midrib (bm) mutants accumulate less and altered lignin relative to non-mutants. Maize bm4-encoded folylpolyglutamate synthase functions to generate the preferred substrate of folate-dependent enzymes, such as bm2-encoded methylenetetrahydrofolate reductase. Consistent with bm4's predicted function upstream of bm2, both mutants display a 7--10% reduction in lignin content and a 16--40% increase in S/G lignin ratio relative to wild-type. This interplay between lignin biosynthesis and various metabolic processes is also seen between lignin and stover carbon emission. As climate change intensifies, the continued accumulation of CO2 in the atmosphere poses potentially irreversible threats to the environment and economy. Exploiting the natural carbon cycle of plants to sequester excess atmospheric C in the soil is a promising strategy for climate remediation. To assess the potential of this approach, stover from over 6,000 maize and sorghum genotypes was incubated in soil and assayed for C emission. While compositional traits, such as lignin, explain up to 48% of variation in C emission, environment still plays a major role. Dynamics of C emission vary across environments and seem to be, at least partially, controlled by the age and lignin content of the stover assayed. Despite environmental influence on C emission, adequate genetic control exists for this trait to allow for moderate heritability estimates and genomic prediction accuracy. Additionally, GWAS for C emission identifies numerous promising candidate genes that could serve as breeding targets for generating varieties with enhanced carbon sequestration potential.