Fig. 5: TPL is expressed in leaf axils and promotes AM initiation.

a Schematic representation of AMs in the WT and the tpl tpr1 tpr4 triple mutant. The diagram is as described in Fig. 1b. Morphology of AMs in the WT (b) and the tpl tpr1 tpr4 triple mutant (c). The plants were grown under short-day conditions for 30 days and then transferred to long-day conditions for 30 days. Scale bars, 1 mm. d–g Cross- and longitudinal sections of shoot apex of WT and the tpl tpr1 tpr4 triple mutant stained with toluidine blue O. A dome-shaped AM was visible in the WT (arrows, d–f) but not in the tpl tpr1 tpr4 triple mutant (yellow arrows, e–g). All the plants were grown under short-day conditions for 30 days. Scale bars, 100 μm. h Expression patterns of pTPL::GFP (green) in the vegetative shoot apex. TPL is expressed in leaf axils (dotted white lines), AMs (arrows) and SAMs (asterisks). The numbers in the upper right corner represent the relative distances from the shoot apex. The plants were grown under short-day conditions for 30 days. Scale bars, 100 μm. i RNA in situ hybridization was used to determine the expression patterns of TPL, TPR1, TPR2 and TPR4 in the vegetative shoot apex of Col-0. Asterisks indicate SAM, arrows indicate AMs, and dotted lines indicate leaf axils. All the plants were grown under short-day conditions for 30 days. Scale bars, 100 μm. j Transverse sections through a vegetative shoot apex showing the distribution of STM and REV mRNAs in the WT and the tpl tpr1 tpr4 triple mutant. STM accumulated in the SAM and AMs (black arrows) of the WT but not in the AMs of the tpl tpr1 tpr4 triple mutant (yellow arrows). REV was found in the AMs of the WT (black arrows), but no signal was detected in the AMs of the tpl tpr1 tpr4 triple mutant (yellow arrows). All the plants were grown under short-day conditions for 30 days. Scale bars, 100 μm. At least three samples were analyzed in (b–j) with similar results for each experiment.