Authors: Jeffrey A. Lacey¹, Thomas H. Ulrich¹, Robert Zemetra², Alexander Karasev², Alan Poplawski², John Carman³

Affiliation: (1) Idaho National Laboratory, (2) University of Idaho, and (3) Utah State University, Caisson Laboratories Inc.

Title: Discovery of genes responsible for apomixis in Sorghum bicolor using virus-induced gene silencing (VIGS)

Abstract: Apomixis, or asexual seed formation, could represent a robust trait delivery and containment platform for agricultural and bioenergy crop plants; however the molecular mechanisms are poorly understood.   Recent gene expression studies have identified several candidate genes expressed differentially in Sorghum bicolor that have apomictic characteristics.  Gene silencing experiments in sorghum, such as virus-induced gene silencing (VIGS), could further elucidate the role each of these genes play in sorghum ovule development.   Barley stripe mosaic virus (BSMV, a tripartite RNA virus) has been used as a VIGS vector to manipulate the expression of genes in other monocots, however methods for its use in Sorghum need to be developed.  In this project, we successfully infected Sorghum using the three BSMV RNA sequences (α, β, and γ-b-GFP) currently used in wheat and barley.  The γ-b-GFP sequence has a green fluorescent protein tag attached to the “b” gene to allow for rapid screening.  These RNA sequences were mixed in equal proportions in an inoculation buffer and rubbed onto the surfaces of sorghum leaves of young and mature plants.  Fluorescence microscopy and western blots were used to determine successful infections.  Here we will present evidence of infection of S. bicolor with BSMV.  Plans for future gene silencing experiments will also be discussed.  Ultimately, this research will characterize the molecular mechanisms that control apomixis in S. bicolor and bring this potentially valuable technology for agricultural and biomass crop improvement closer to implementation in the field.