Homeodomain protein underpins leaf shape variation in cotton ($)

Homeodomain transcription factors are well-known as regulators of developmental patterning, including in leaves. Andres et al. examine the molecular basis behind leaf shape in cotton, particularly the Okra locus that was identified by breeders as a regulator of leaf shape. They show that the Okra locus encodes a homeodomain transcription factor, and that different leaf shapes (including normal, okra, super-okra and sub-okra) express allelic variants. Specifically, the narrower okra and super-okra leaves express higher levels of the gene. Suppressing this expression through viral-induced gene silencing transiently switches leaf shape to the broader normal form, demonstrating the importance of this gene in the control of leaf shape. As leaf shape is correlated with water-use efficiency, light interception and susceptibility to insects, these insights provide breeders with new tools. This paper would be a nice addition to a genetics course, especially if provided to students along with some of the classic studies of the Okra locus, such as Shoemaker (1909) and Green (1953). (Update: Author Dan Chitwood also recomments Hammond 1941a and 1941b for teaching).  Proc. Natl. Acad. Sci. USA 10.1073/pnas.1613593114