Gilad Gabay: ggabay@bgu.ac.il, Junli Zhang: psjzhang@ucdavis.edu, Tzion Fahima: tfahima@evo.haifa.ac.il, Jorge Dubcovsky: jdubcovsky@ucdavis.edu

Wheat is an essential crop for global food security and is well adapted to a wide variety of soils. However, new stresses imposed by climatic change require new tools to optimize root architectures for changing environments. We previously reported the identification of a cluster of monocot-specific 12-OXOPHYTODIENOATE REDUCTASE genes from subfamily III (OPRIII) that modulate differences in wheat root architecture through the regulation of the jasmonic acid (JA) signaling pathway. However, the gene networks regulating different root architectures and their impact on grain yield under water-limited conditions remain poorly understood.

In this study, we characterize a new QTL for root architecture that interacts with the OPRIII genes. We found that the triplicated OPRIII locus present in the recombined wheat-rye chromosome 1RW is associated with short roots in Hahn but not in the Pavon background. In the F2 progeny of a cross between Hahn-1RW and Pavon-1RW, we identified a significant QTL for root length on chromosome 4B (Qrln.ucw-4B).

We demonstrated a significant interaction between this QTL and 1RW using a second F2 population from the cross Pavon-1RW x Hahn-1RS and a BC4F2 population segregating for both loci in the Hahn background. Using heterogeneous inbred families (HIFs) from a Pavon-RW x Hahn-RW F5 line, we narrowed down the Qrln.ucw-4B to 6.37 Mb interval including 49 candidate genes.

We further investigated these genes and their interactions with the 1RW locus using multiple transcriptome analyses of wild-type and transgenic lines over-expressing OPRIII. These analyses identified a short list of candidate genes with potential interactions with OPRIII genes for the regulation of root development in wheat.

These genes include key regulators in the JA-signaling biosynthetic pathways and ethylene phytohormones. The OPRIII genes and their interactions provide a useful entry point to engineer root architecture in wheat and potentially other cereals.