Scientists from the National Agriculture and Food Research Organization of Japan and partners showed that DEEPER ROOTING 1 (DRO1) homologs could be useful for the controlled breeding of root system architectures that are adapted to abiotic stress conditions caused by climate change. The research article is published in Proceedings of the National Academy of Sciences of the USA (PNAS).

The root system architecture (RSA) of crops can have an impact on their production, especially when exposed to abiotic stress conditions such as drought, waterlogging, and salinity. Thus, through cloning and characterization of qSOR1 (quantitative trait locus for SOIL SURFACE ROOTING 1), a homolog of DRO1 (DEEPER ROOTING 1) that control RGA, a shallower root growth angle (RGA) could improve rice yields in saline paddies.

CRISPR-Cas9 assays showed that other homologs of DRO1 are also linked to RGA. Results indicated that natural versions of the DRO1 homologs could be used to regulate RSA variations in rice. In saline paddies, near-isogenic lines with qSOR1 loss-of-function allele had soil-surface roots which allowed the rice plants to sidestep the reducing stresses of saline soils, leading to better yields compared to the parental cultivars without SOR.

Read more findings in PNAS.

See: https://www.pnas.org/content/early/2020/08/13/2005911117/tab-figures-data

Figure: Phenotypic and molecular characterization of qSOR1. (A) Graphical genotypes of Sasanishiki (SA; Left), qsor1-NIL (NIL; Center), and Gemdjah Beton (GB; Right). The white and black rectangles indicate the homozygous regions from SA and GB, respectively. Red arrowhead, position of qSOR1. (B) Images of rice plants grown in small cups for 20 d after sowing and after the removal of the topsoil from each cup. (C) Images of the basal parts of the rice plants grown in the cups in B. The root growth angle (θ_rga) of each plant was determined by measuring the angle between the horizontal line and the shallowest nodal root. (D) Mean root growth angle of SA, qsor1-NIL, and GB. Data are means + SD; n = 40, 38, and 36 plants for SA, qsor1-NIL, and GB, respectively. Different letters indicate significant differences (P < 0.01, Tukey’s HSD test). (E) Sequence variations between SA and GB in the two putative ORFs detected in the candidate region of the qSOR1 locus. Red arrowhead, a single 1-bp substitution. Orange rectangles, ORF; gray rectangles, 5′ and 3′ UTRs. (F) qSOR1 expression in various shoot and root tissues. Samples of the root tips from different depths, leaf blades, leaf sheaths, and shoot bases (1-cm sample from the bottom of the shoot) were taken from plants grown in baskets, 30 d after sowing. Expression of qSOR1 was normalized to that of rice Ubiquitin gene. Data are shown as mean + SD; n = 3 biological repeats. P values are based on Student’s t tests. (G) Gravitropic curvature in the seminal roots of SA and qsor1-NIL plants. θ_rac is the root angle of the curvature after rotation. Asterisks indicate the positions of the root tips at the start of the rotation. Yellow arrows indicate the direction of the gravitational force. (H) Root angle of the curvature of SA and qsor1-NIL after rotating 90° from the original vertical axis for 4 h. P value is based on Student’s t test. (Scale bars: 1 cm.).