An Improved Mesocotyl Elongation Assay for the Rapid Identification and Characterization of Strigolactone-Related Rice Mutants

Abstract

Strigolactones (SLs) constitute an important class of plant hormones involved in diverse developmental activities in plant growth and host-parasite interaction. Although substantial progress has been made to understand this pathway, the mechanism of action is still elusive especially with its interaction with other phytohormones and downstream targets. Here we have utilized the negative role of strigolactones in rice (Oryza sativa L.) mesocotyl elongation as a morphological marker for the identification and characterization of new developmental mutants. We observed that deep sown seeds develop longer mesocotyl compared with the surface-grown seeds in the dark condition. Based on this observation, we have developed a method to access mesocotyl elongation consisting of the glass vessel and vermiculite as a growth media. Mesocotyl elongation in the modified deep sown system results in a many-fold increase compared to the surface-grown seeds in the dark condition. External application of SLs analog rac-GR24 rescued the elongated mesocotyl phenotype in the mutant defective in SLs synthesis but not the signaling mutant, demonstrating its applicability in the physiological experiments. The modified mesocotyl elongation assay can be used as a rapid method for characterization and identification of suppressors/enhancers and new developmental mutants in the SLs or its associated pathway saving a huge amount of time and space.