Functional characterization of petiolule-like pulvinus (PLP) gene in abscission zone development in Medicago truncatula and its application on alfalfa improvement

Abstract

Organ abscission plays an important role in plant development. To date, little is known about genes involved in leaf abscission zone differentiation. Leaf loss during the haymaking process in alfalfa (Medicago sativa L.) affects forage yield and quality, resulting in tremendous economic loss in the United States. The objective of this study is to analyze the role of the petiolule-like pulvinus (PLP) gene in leaf abscission zone (AZ) differentiation and apply our knowledge of PLP on alfalfa improvement to decrease leaf loss during the haymaking process. Detailed characterization of plp mutants in the model legume Medicago truncatula at the phenotypic level (shaking and breakstrength assay), microscopic level (scanning electron microscopy and cross section analysis) and molecular level (expression pattern by GUS staining) revealed that the loss-of-function of PLP resulted in an absence of AZ formation, and PLP is involved in leaflet and petiole AZ differentiation. Microarray analysis indicated that PLP is associated with auxin-related genes. Down-regulation of the MsPLP in alfalfa (Medicago sativa) altered the pulvinus region to petiolule-like structure and led to increased leaflet breakstrength, which offers a new approach to decrease leaf loss during the haymaking process. This study demonstrates how knowledge gained from a model plant can be applied to the genetic improvement of a commercially important crop.