MIK2 controls root angle in a THE1- and cellulose synthase complex-dependent manner.

<p>(A-D) Nine-day-old Arabidopsis seedlings grown in an upright position (under a 10° angle relative to the direction of gravity) on MS agar medium with 1% sucrose. Pictures were taken from the front of the plate. (A-C) The growth medium contained DMSO (mock) (A), 2 nM ISX (B), or 25 μM DCB (C). (A) The white arrow indicates skewing of <i>mik2-1</i> roots relative to the vertical growth axis. (A-D) Root angle was quantified; a positive value indicates skewing to the left, while a negative value indicates skewing to the right. Error bars represent standard error of n = 15 biological replicas. Different letters indicate statistically significant differences between genotypes (ANOVA and Holm-Sidak test (<i>p</i> < 0.05)). The experiments were repeated at least three times with similar results.</p

MIK2 is required for resistance to the fungal root pathogen <i>Fusarium oxysporum</i> in a THE1-independent manner.

<p>(A,B) Percentage of chlorotic leaves per plant (A), and percentage of decayed plants (B) after infection of the roots with <i>F</i>. <i>oxysporum</i> isolate Fo5176. (A) The percentage of chlorotic leaves per plant was counted 10 days after inoculation with <i>F</i>. <i>oxysporum</i> spores. (B) The number of decayed plants was counted 3 weeks after inoculation with <i>F</i>. <i>oxysporum</i> spores. (A,B) The bars represent the average of four independent experiments, each consisting of n = 20–40 plants per genotype. Error bars represent the standard error of n = 4 experiments. Different letters indicate statistically significant differences between genotypes (ANOVA and Holm-Sidak test (<i>p</i> < 0.05)). No disease symptoms were observed on mock-inoculated plants for any of the genotypes (n = 10). (C) Representative pictures of the different genotypes in (A) and (B) after <i>F</i>. <i>oxysporum</i> infection.</p

Inhibition of cellulose biosynthesis induces immune marker gene expression.

<p>(A,B) Immune marker gene expression in 13-day-old Arabidopsis seedlings determined by qRT-PCR. (A) Seedlings were mock- or ISX-treated (0.6 μM) for the indicated periods. (B) Seedlings were mock treated, or treated with 0.6 μM ISX, 6 μM DCB, 0.4 μM TXT, or 400 mM Mannitol (Man) for 9 h. (A,B) Expression of the immune marker genes <i>FRK1</i>, <i>At1g51890</i>, and <i>CYP81F2</i> was normalized relative to <i>U-box</i> expression values. Depicted is the fold change in expression relative to time point t = 0h (A), or relative to mock treatment (B). Error bars represent standard error of three technical replicas. Experiments were repeated at least three times with similar results.</p

MIK2 is required for salt stress tolerance in a THE1-dependent manner.

<p>(A) Ten-day-old Arabidopsis seedlings were grown in an upright position on ½ MS agar medium without sucrose, supplemented with or without 75 mM NaCl or 150 mM sorbitol. Depicted is the change in the angle of the root after NaCl or sorbitol treatment compared to mock treatment; the negative value indicates a change to the right. Error bars represent standard error of n = 20 biological replicas. The experiment was repeated three times with similar results. (B) Dry weight of NaCl-treated plants as percentage of the dry weight of untreated plants. (Absolute dry weight is depicted in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1006832#pgen.1006832.s010" target="_blank">S10 Fig</a>). One week after germination, plants were transferred to pots with soil watered from below with or without 75 mM of NaCl in rainwater. After 4 weeks of treatment the rosettes were cut, and dry weight was determined. The experiment was repeated three times with similar results, data were pooled and the average is depicted. Error bars represent the standard error of n = 60 plants. (A,B) Different letters indicate statistically significant differences between genotypes (Kruskal-Wallis ANOVA on ranks followed by Dunn’s multiple comparison procedures (<i>p</i> <0.05)).</p

The LRR-RK MIK2 and CrRLK1L THE1 are major regulators of responses triggered by cellulose biosynthesis inhibition.

<p>(A) Immune marker gene expression in 13-day-old Arabidopsis seedlings determined by qRT-PCR. Seedlings were mock treated, or treated with 0.6 μM ISX, 6 μM DCB, or 0.4 μM TXT for 9 h. Expression of the immune marker genes <i>FRK1</i>, <i>At1g51890</i>, and <i>CYP81F2</i> was normalized relative to <i>U-box</i> expression values. Depicted is the fold change in expression relative to mock treatment. Error bars represent standard error of three technical replicas. (B-E) JA (B) and SA production (C) and lignin-deposition (D,E) in 6-day-old Arabidopsis seedlings, mock treated or treated with 0.6 μM ISX for 7 h (B,C) and 12 h (D,E). Error bars represent standard error of n = 4 (B,C) or n = 20 (E) biological replicas. (B) The upper and lower panel display the same data, yet in the lower panel, the y-axis has been adjusted to visualize the JA levels in mock-treated samples. (D) The size bar represents 100 μm. (A-E) Asterisks indicate a statistically significant difference relative to Col-0, as determined by a two-tailed Student’s <i>T</i>-test (<i>p</i> < 0.05). Experiments were repeated at least three times with similar results.</p