Extended Data Fig. 9: Repression of HD-ZIP III-target genes by ZPR2 induction and stabilization occurs in the shoot apex.
From: An apical hypoxic niche sets the pace of shoot meristem activity
a, Effect of ZPR2 and ZPR2–GUS on the transactivation activity of REV on the ZPR1 promoter. These data indicate that ZPR2 is not able to repress REV activity when fused with a GUS reporter protein at its C terminus. One-way ANOVA, followed by Holm–Sidak post hoc test; n = 5 protoplast pools. b, Schematic of the construct that provided oestradiol-inducible expression of ZPR2, and after protein stabilization under hypoxic conditions. c, Separate and combined effect of oestradiol (50 μM) application, for 4 h before exposure to 2% O2 for 24 h, on the expression of a GUS reporter under the control of pHEC1 (HECATE 1) and pPSK5 (PHYTOSULFOKINE 5 PRECURSOR) promoters in 6-day-old Arabidopsis seedlings that also expressed an oestradiol-inducible ZPR2 construct. Seeds of these genotypes were obtained as F1 offspring that were generated by crossing homozygous promoter:GUS lines with homozygous oestradiol-inducible ZPR2 (pMDC7:ZPR2) plants. The observation was repeated twice. A reduction in pPSK5 or pHEC1 activity by combined ZPR2 induction and hypoxia was observed in a total of 8 out of 12 and 15 out of 20 plants, respectively. d, Effect of oestradiol-mediated induction of ZPR2 and its stabilization by hypoxia on pTAA1:GUS staining in five-day-old wild-type and transgenic pMDC7:ZPR2 plants. Twenty-four hours of hypoxia, but not oestradiol treatment (50 μM), was sufficient to repress pTAA1-driven GUS expression in the wild-type background, probably via stabilization of the endogenous ZPR2 protein (2 out of 3 plants). The hypoxia treatment also inhibited expansion of the first pair of true leaves. Stimulated ZPR2 expression in the pMDC7:ZPR2 background further decreased pTAA1:GUS staining (3 out of 3 plants). This experiment was performed once.
