SBT3.5 Antibody

Mechanism of Action

SBT3.5 processes PME17, a group 2 PME involved in pectin demethylesterification. This cleavage releases the active PME domain into the apoplast, modulating cell wall plasticity. Key steps include:

1. Co-expression: SBT3.5 and PME17 transcripts overlap spatially in root tissues .

2. Proteolytic cleavage: Transient co-expression assays in Nicotiana benthamiana confirmed SBT3.5-dependent processing of PME17 at the RKLL motif (Fig. 1) .

3. Functional consequence: Processed PME17 alters pectin methylesterification, influencing root growth and stress adaptation .

Genetic and Phenotypic Analysis

Mutants exhibited reduced PME activity and impaired root architecture, linking SBT3.5 to pectin-mediated growth regulation .

Biochemical Evidence

• Western blotting: Co-expression of SBT3.5 and PME17-myc in tobacco revealed a shift from full-length PME17 (61 kDa) to processed isoforms (35–38 kDa) .

• Inhibitor assays: Kazal-type inhibitors (EPI1/EPI10) blocked SBT3.5 activity, confirming its proteolytic role .

Functional Implications

• Root development: SBT3.5 fine-tunes PME17 activity to balance cell wall rigidity and flexibility, critical for lateral root emergence .

• Stress adaptation: SBT3.5-mediated processing may prime plants for responses to osmotic stress, though this role is less characterized compared to homologs like SBT3.8 .

Experimental Workflow

1. Gene knockout: T-DNA insertions in sbt3.5–1 (SAIL_400F09) and sbt3.5–2 (GABI_672C08) were validated by qPCR .

2. Protein interaction: Co-immunoprecipitation and mass spectrometry confirmed SBT3.5-PME17 interaction in root cell wall extracts .

3. Phenotyping: Mutants showed reduced fresh weight (20–30% decrease) and aberrant root hair patterning .

Open Questions and Future Directions

• Regulatory networks: How SBT3.5 expression is modulated by upstream signaling (e.g., MAP kinases) .

• Broader substrates: Identification of additional SBT3.5 targets beyond PME17.