Fig. 2: Exo70A1 functions in xylem vessel development and hydraulic conductivity.

a Interacting proteins identified by immunoprecipitation-mass spectrometry (IP-MS) of Exo70A1-OE plants. b Cryo-electron microscopy structure of the exocyst complex²⁸ (PDB ID: 5YFP). Subunits identified are color-coded based on the IP-MS score; undetected subunits are gray. c Cleared sheath tissue stained with toluidine blue. The red arrow indicates lignified annular secondary cell wall (SCW) thickenings in protoxylem. Scale bars, 30 μm. d Distance between two adjacent annular thickenings. n = 90 distances between two adjacent annular thickenings measured from 3 plants. e Semi-thin cross-sections of primary roots. Scale bars, 100 μm. f Root hydraulic conductivity (Lp_r) regression slope, based on 3 replicated experiments. g Dye uptake and movement assay using stems of 14-day-old seedlings. Red arrows indicate dye front. h Rate of dye movement. n = 9 plants. i Scanning electron microscopy (SEM) images of stem vascular bundles. Red asterisks highlight undifferentiated vessels. Px, protoxylem; Mx, metaxylem. j Percentage of abnormal vascular bundles per genotype. k Xylem vessels area for indicated genotypes. n = 9 vascular bundles from 3 plants. l Pitted metaxylem vessels stained with Direct Red in the indicated plants (with identical genetic background of WT). Scale bar, 100 μm. m Length of pitted vessels. n = 50 vessels from 3 plants. n Schematic of metaxylem vessel longitudinal section. PCW, Primary cell wall. o Transmission electron microscopy (TEM) of root metaxylem vessel longitudinal sections. Brown and green lines delineate SCW thickenings and PCWs. XPs, xylem parenchyma cells. Scale bars, 2 μm. Thickness (p) and adjacent distance (q) of SCW thickenings in root metaxylem vessels. n = 60 SCW thickenings from 3 plants in p. n = 60 distances between two adjacent SCW thickenings from 3 plants in q. In e, and i, the experiment was repeated at least three times, and a representative image was selected for display. In d, f, h, j, k, m, p, and q, data are presented as mean ± SD; p-values were obtained by two-sided Student’s t-test. In c, e, g, i, l, and o, representative images are shown.