Fig. 1: GA induces secondary xylem proliferation and vessel expansion.
From: Gibberellins promote polar auxin transport to regulate stem cell fate decisions in cambium
a, Cross-sections after a 10 day GA treatment in 4-day-old Col-0 and ga1 roots. Black dotted lines indicate the most recent cell divisions. Red dotted lines mark the border between the phloem and the periderm. b–e, Quantifications of secondary vessel (b) and xylem parenchyma cell numbers (c), individual secondary vessel area (d) and total phloem cell number (e) in 14-day-old seedlings. f–h, Lineage tracing with pHS:Dbox-CRE x 35S:lox-GUS (HSdCR) in active cambium with GUS-stained sectors (blue) originating from a single recombination event. Recombination was induced in 16-day-old seedlings, after which they (Col-0 in f and g and ga1 in h) were grown for 6 days under mock (f and h) or GA4,7 conditions (g). Black arrowheads indicate the most recent cell divisions in the sectors (thinnest cell wall). i, GUS sectors (bars) plotted relative to the position of the thinnest cell wall (yellow line) in each sector. Values indicate average number of phloem and xylem cells (± s.d.) within the sectors. j, Confocal cross-sections of pAPL:erRFP after an 11 day GA or mock treatment in 4-day-old plants. k, The ratio of cells expressing APL versus all phloem cells in j. In b, c, e and k, the boxes in the box-and-whisker plots show the median and interquartile range, and the whiskers show the total range. In the violin plots in d, the white dot shows the median and the thick line the interquartile range. The thinner line represents the rest of the distribution. Each side of the line is a kernel density estimation that shows the distribution shape of the data. In b–e and k, individual data points are plotted as purple dots. Numbers in b–e and k indicate number of samples. Two-way ANOVA with Tukey’s post hoc test in b–e and one-way ANOVA with Tukey’s post hoc test in k. Boxes/bars not sharing a lower-case letter in the plots indicate a significant difference, P < 0.05. Scale bars, 50 µm (a), 20 µm (f–h) and 10 µm (j). p, phloem; pp, primary phloem pole; x, xylem; v, secondary xylem vessel. All experiments were repeated three times.
