Kn1

Kn1, also written Kn1 or knotted1, is a maize gene encoding a homeobox transcription factor of the KNOTTED-like (KNOX) family. It was identified as a key regulator of shoot meristem function and leaf morphogenesis. The wild-type Kn1 gene helps maintain the activity of the shoot apical meristem and influences leaf development by controlling cell division and differentiation at the leaf base. Mutants display abnormal leaf morphology and meristem-related defects, which gave the gene its name.

Molecularly, Kn1 encodes a nuclear-localized transcription factor containing a homeobox domain that binds DNA and regulates downstream targets. As a member of the KNOX family, Kn1 participates in a regulatory network that modulates hormone balance, typically promoting cytokinin biosynthesis and signaling while repressing gibberellin biosynthesis. This hormonal balance supports meristematic activity and delays differentiation, contributing to proper plant architecture.

Developmentally, Kn1 activity is crucial for maintaining shoot meristem identity and shaping leaf form. Altered expression can lead to changes in leaf complexity or outgrowths, reflecting its role in defining growth boundaries between meristematic tissue and developing leaves. In maize and related species, Kn1 interacts with other transcription factors, including BELL-type homeobox proteins, within a conserved regulatory network that governs organ patterning.

Broader context places Kn1 among the knotted1-like (KNOX) genes found across plants. Homologs in many species participate in meristem maintenance and leaf development, with functional diversification contributing to species-specific plant architecture. The Kn1/KNOX family remains a central focus in studies of plant morphogenesis and crop improvement.