Submitted to: Gordon Research Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 25, 2010
Publication Date: July 21, 2010
Citation: Sullivan, M.L. 2010. Molecular Biology Approaches to Solve Forage Crop Limitations: Improving Protein Utilization and Preventing Leaf Loss in Alfalfa [abstract]. Gordon Research Conference on Plant Molecular Biology, July 18-23, 2010, Holderness, New Hampshire. Technical Abstract: Our laboratory is using molecular biology approaches to better understand and develop solutions to some of the current limitations of alfalfa and other forage crops used in animal and bioenergy production systems. A major limitation of alfalfa is that much of its protein is degraded during harvest and storage. Since ruminant animals poorly utilize degraded protein, this has significant economic and environmental impacts. In red clover, post-harvest oxidation of o-diphenol caffeic acid derivatives to o-quinones by an endogenous polyphenol oxidase (PPO) prevents breakdown of forage protein during storage. We are using molecular biology approaches to transfer this natural system of protein preservation to alfalfa. Our recent work focuses on the biosynthetic pathway for phaselic acid (caffeoyl-malate), the major o-diphenol substrate for PPO in red clover. We have recently identified a novel transferase that is crucial for phaselic acid accumulation in red clover. Expression of this transferase in alfalfa leads to accumulation of phaselic acid and related hydroxycinnamoyl-malate esters. This result suggests it should be possible to recreate the PPO/o-diphenol protein preservation system in alfalfa. A second limitation of alfalfa is loss of up to 25% of biomass due to abscission of lower, canopy-shaded leaves. Retention of this highly digestible biomass through harvest would greatly benefit both animal and bioenergy production systems. To better understand leaf abscission in alfalfa, we have used abscission-associated genes identified in arabidopsis and other model systems to identify potential homologs in the closely related alfalfa relative, Medicago truncatula. By using promoter::GUS fusions, we have determined that some of these candidate genes are expressed in an abscission zone-specific manner in alfalfa. The next steps will be to use ectopic expression and RNAi-mediated gene silencing to examine the in vivo functions of the products of these genes.