UC Davis

Understanding carotenoid metabolism in staple crops is crucial to improving crop performance and nutritional content. In a specific application, biofortification of provitamin A carotenoids such as β-carotene in staple crops such as wheat presents a promising solution to address nutritional issues worldwide. However, manipulation of carotenoid metabolism in wheat without compromising plant performance in an agronomic setting is critical to achieve widespread adoption and impact. Carotenoid biosynthetic enzymes are suitable targets for manipulation to optimize carotenoid profiles to achieve these aims. The research presented in this dissertation focuses on the functional dissection of a group of carotenoid β-hydroxylases in wheat and the evaluation of tetraploid wheat lines in which provitamin A biofortification was achieved. An extension of this research portfolio is presented here also that showcases the potential that our research program has for the engagement of learner communities around issues of food security.

The first research chapter enclosed presents a functional dissection of carotenoid β-hydroxylases (HYDs) in wheat, key enzymes involved in the biosynthesis of xanthophylls through the hydroxylation of β-rings of carotenes. By elucidating the roles of individual HYDs in wheat, this chapter aims to uncover the functional specialization and redundancy that exists within the HYD genes and their subgenome homoeologs in tetraploid wheat. Substantial functional redundancy was observed, though leaf- and grain-specific roles were uncovered for homoeologs of HYD1 and HYD2, respectively. HYD2 homoeologs also showed a considerable, developmental-stage specific role in salt stress response that is discussed in the third research chapter of this dissertation.The second research chapter evaluates the field agronomic performance of tetraploid wheat lines with enriched β-carotene concentrations in the grains. Assessments of agronomic traits, yield parameters, and nutritional quality have been conducted, which supply a comprehensive understanding of the performance of the biofortified lines under field conditions. Overall, no considerable impacts on agronomic performance were identified in the biofortified lines, and the β-carotene enrichment observed under semi-controlled conditions was found to be higher when the lines were cultivated in a field setting.

The fourth research chapter showcases the translation of our research program into an educational setting using scientific teaching approaches in the classroom. By developing educational materials and implementing innovative teaching methodologies, this chapter showcases the potential for food security and plant biochemistry to serve as a context around which classroom discussions of global issues can be anchored. This chapter includes a high-level overview of underutilized cereal and pseudocereal grain crops (a lesson module subject), a lesson module surrounding these crops, and our further application of scientific teaching principles to a collaborative online international learning module centered on medicinal plants.