Overexpression of AGAMOUS-like gene PfAG5 promote early flowering in Polypogon fugax

Abstract

Background: Herbicides are the major tool for controlling large populations of yield depleting weeds. However, overreliance on herbicides has resulted in weed adaptation and herbicide resistance. In recent years, early flowering weed species related to herbicide resistance is emerging, which may cause seed loss before crop harvest, creating a new problem for non-chemical weed management. However, mechanisms regulating early flowering in weedy species is rarely investigated. Results: The MADS-box gene family plays an important role in flowering time regulation and floral organogenesis. In this study, a homolog gene of AGAMOUS sub-family (referred to as PfAG5) of the MADS-box family was cloned from plants of an early flowering Polypogon fugax population resistant to the ACCase inhibitor herbicide (clodinafop-propargyl). The PfAG5 gene was functionally characterized in Arabidopsis thaliana. Over-expression of the PfAG5 gene in Arabidopsis resulted in early flowering with abnormal flowers (e.g. small petals, short plants and reduced seed set) compared to the wild type. The expression of the PfAG5 gene was high in leaves and flowers, but low in pods in transgenic Arabidopsis. The PfAG5 gene was earlier and higher expressed in the resistant (R) than the susceptible (S) P. fugax plants. Furthermore, one protein (FRIGIDA-like protein) interacting with PfAG5 in R P. fugax was identified by the yeast two-hybrid system with relevance to flowering time regulation. Conclusions: These results suggest that the PfAG5 gene is prominently involved in modulating early flowering in P. fugax. This study provides the first evidence for the regulation mechanism of early flowering in an herbicide resistant weed species.