MAKR2 Regulates the Pace of the Root Gravitropic Response
(A) qRT-PCR analyses of MAKR2 expression in 2x35Sprom::MAKR2-2xmCherry (MAKR2-Ox1), 2x35Sprom::MAKR2-mCitrine (MAKR2-Ox2), and amiMAKR2.1 lines relative to MAKR2 expression in wild-type seedlings (mean ± SEM).
(B) Pictures showing the root phenotypes of the genotypes indicated at the bottom and related quantification of the horizontal growth index (Tukey boxplot). Plants were grown at a 45° angle with respect to the vertical axis. Scale bars represent 5 mm.
(C) DR5prom::GUS accumulation pattern in the absence and after 5 h of gravistimulation at a 135° angle in wild-type and MAKR2-Ox1 plants and related quantification (Tukey boxplot). The white asterisks indicate the arrow-like pattern observed in MAKR2-Ox1 lines; the white arrow indicates the asymmetric GUS signal observed after gravistimulation in the wild type. Scale bars represent 50 μm.
(D) Representative pictures of the root gravitropic curvature 48 h after reorienting seedlings at a 135° angle and related quantification of root gravitropic bending over time (mean ± SEM). Scale bars represent 2 mm. See Figure S1F for a statistical comparison.
For the horizontal gravitropic index and the kinetics of the gravitropic response, a linear model was fitted on measurements from wild-type plants and the different mutants using lm() function from stats package available in R software (https://www.r-project.org/). This model estimates a weight for each variable (wild-type and mutant plants) and the associated probability that such weight is different from zero based on a t test. The probability derived from the t test is the p value in this comparison and significant differences were considered when p < 0.05. See also Figure S1.