Shoot organs, including leaves, emerge from the shoot apical meristem throughout plant development. Leaves can take on diverse forms, from smooth simple shapes to lobed complex morphology, depending on the nature of patterning about the leaf margin. These processes vary according to species, developmental stage, and environmental conditions thereby allowing a plant to thrive in its ecological niche.
In the past, it has been suggested that the BLH homeodomain transcription factors SAWTOOTH1 and SAWTOOTH2 repress serrations in Arabidopsis thaliana by promoting a transition to deterministic cell fate about the leaf margin1. Here, we extend upon this knowledge to suggest that SAW1 and SAW2 interact with the Class II KNOX transcription factor KNAT3 in Arabidopsis development.
Foremost, SAW1 and SAW2 expression overlaps with KNAT3 expression in the adaxial margin of the young leaf, while saw1 saw2 knat3 plants display an enhanced serration phenotype relative to saw1 saw2 plants. KNAT3, expressed under its native promoter, can rescue this effect. Interestingly, when KNAT3 is over or mis-expressed in saw1 saw2 knat3 plants, serrations are again exaggerated beyond what is observed in the triple mutant. KNAT3 acts in repressing serrations when expressed in its native domain but promotes serrations on the abaxial side of the leaf in the absence of SAW1 and SAW2.