Fig. 4: BAK1 contributes to ALR1-mediated Al resistance and signaling.
From: The LRR receptor-like kinase ALR1 is a plant aluminum ion sensor
a–d Root growth under control and Al treatments (a, c), and their relative quantification (b, d) (n = 19–24). The average length of each genotype was set to 100%, and the relative root length was expressed as a percentage (root length with Al treatment/root length without Al × 100). e Expression of ALMT1 in roots under control and Al (25 µM) treatments for 6 h (n = 3). f Malate secretion from roots under control and Al (25 µM) treatments for 24 h (n = 3). g, h GFP-STOP1 fluorescence signals in roots (g) and their relative quantification (h) (n = 15). i Bimolecular fluorescence complementation (BiFC) mediated detection of interaction between ALR1 and BAK1, ALR1ED-TM-PSYR1CD (a chimeric ALR1 comprised of ALR1 extracellular and transmembrane domains and the cytoplasmic domain of another RLK PSY1R) and BAK1, or ALR1 and BAK1ED-TM (BAK1 extracellular domain and transmembrane domain), respectively, following control, Al (50 µM) or La (50 µM) treatments for 10 min. j Relative fluorescence intensity in i (n = 40). k Co-immunoprecipitation (Co-IP) showing the interaction between ALR1 and BAK1 in protoplasts following control or Al (50 µM) treatments for 10 min. l Inter-phosphorylation of ALR1CD and BAK1CD in response to different concentrations of Al (0, 10, 50 and 100 nM) in vitro. m BAK1CD promotes the phosphorylation of RbohDN by ALR1CD under both control and 100 nM Al treatment conditions. The arrow indicates a phosphorylated RbohDN band detected with pS39 antibodies. The asterisk indicates that pS39 antibodies can also unexpectedly recognize the BAK1 cytoplasmic domain (but cannot recognize other cytoplasmic domains, data not shown). n The effect of PSK (3 µM) on in vivo RbohD phosphorylation. Bars = 1 cm (a, c), 100 µm (g), 20 µm (i). All data were analyzed by unpaired t-test (b, d–f, h, j) (ns non-significance, *P < 0.05, **P < 0.01, ****P < 0.0001).
