DEEPER ROOTING 1 Controls Root Architecture in Arabidopsis and Prunus Species

Root system architecture (RSA) influences plant productivity by providing uptake of water and nutrients, biotic soil interaction, and soil anchorage. For tree crops, breeding or engineering for RSA traits in rootstocks is an important target for improving productivity and yields. Defined at the spatial distribution of roots in soil, the RSA of a plant is determined by factors such as primary and lateral root growth rates, lateral root branching, and root orientation. DEEPER ROOTING 1 (DRO1) was recently identified in rice to affect root orientation and overall root system depth. Its expression led to deeper roots, allowing for improved grain filling and yields under water-deficit. Using this trait in dicot rootstocks may prove advantageous for survival in drier climates. Based on sequence analysis we have placed DRO1 and DRO1-related genes within the IGT family, which contains genes known to influence lateral branch orientation in shoots. We took a multi-species approach, using our transgenic tools in plum and leveraging the speed and tools of the model system Arabidopsis, to elucidate the role of DRO1 in dicot species. Here we report that PpeDRO1expression in peaches is strongest in root tissues, and in transgenic plum lines overexpression of peach DRO1 results in longer root systems, as well as the ability to develop roots on tissue culture shoot media. Similarly, AtDRO1 in Arabidopsis is root-specific and strongest near lateral root (LR) tips, while remaining restricted from LR primordia and newly emerging LRs. Loss of AtDRO1 leads to wider LR angles and shorter primary roots compared to controls, while overexpression lines have steeper angles. We are currently employing a yeast-2-hybrid approach to search a library of peach proteins for PpeDRO1 interactors, and an RNA-seq approach in Arabidopsis to survey downstream effects of DRO1 loss. Taken together we hope to piece together a mechanistic picture of how DRO1 controls LR angle and root depth in dicot species.