Fig. 4: A thicker epidermis and thinner cortex cell wall model facilitates rice root adaption to compaction.
From: Ethylene modulates cell wall mechanics for root responses to compaction
a,b, Longitudinal (a) and cross-sectional (b) schematics showing TEM and AFM measurement locations in cortex (blue) and epidermis (red) of rice root cells. c, TEM images showing wall thickness (red lines) in root epidermis and cortex of five-day-old wild-type, arf1-1, OE-ARF1, cesa6 and arf1cesa6 seedlings grown in normal and dense media. Scale bars, 200 nm. d,e, Epidermal (d) and cortical (e) wall thickness statistical analysis (n = 300, 15 points from 20 cells, 1 of 5 replicates) was performed using two-way ANOVA followed by Tukey test. P (interaction) < 0.0001. f,g, Root cortical (f) and epidermal (g) wall stiffness in wild type, arf1-1, OE-ARF1, cesa6 and arf1cesa6 seedlings in dense media (n = 15 test points, 1 of 4 replicates; two-sided P values from Dunnett test). h, Expression of ARF1, CESA5, CESA6 and CESA8 in the elongation zone of Nip and ein2 seedlings grown under normal (N) and dense (D) media for five days (one of three replicates, two-sided P values of Welch’s t-test with Bonferroni–Dunn method are shown). Bars show mean ± s.d. i,j, Root cortical (i) and epidermal (j) wall stiffness of Nip, ein2 and eil1eil2 plants grown in dense media (n = 17 plants, 4 replicates; two-sided P values from Dunnett test). Box plots in d,g,i,j show median (centre), 25th–75th percentiles (box), and minimum to maximum range (whiskers). Different letters indicate significant differences (P < 0.05) in d,e. k, Soil compaction and ethylene induce OsARF1 expression mainly in cortex cells, suppressing primary wall CESA expression. Reduced cellulose biosynthesis causes radial expansion of cortex cells and root swelling due to decreased cortical wall thickness. By contrast, epidermal wall thickness and stiffness are maintained to support root penetration in compacted soils. Colour intensity denotes cell wall thickness.
