Figure 9.

Proposed model for SYP121-related secretory traffic, the interaction between SYP121 and SEC11, and their uncoupling by the SYP121^R20AR21A mutant. Wild-type plants (Columbia-0 [Col-0], green arc) utilize SEC11 in facilitating SYP121 activation for interaction with VAMP721 and the K⁺ channels, stabilizing the SNARE complex for vesicle fusion, and the SEC11^Δ149 fragment competes to prevent SNARE complex disassembly (Honsbein et al., 2009; Karnik et al., 2013b, 2015; Grefen et al., 2015; Zhang et al., 2015). In the syp121 mutant complemented with SYP121^R20AR21A, SEC11 binding for SNARE complex assembly with SYP121 is blocked, although K⁺ channel activation by the Qa-SNARE is retained, thereby suppressing SYP121-associated traffic but not K⁺ channel activity.