Josh Strable
Cornell University

In the seminar, I will present my current postdoctoral work that uses leaf development and the phytohormone ethylene to explore questions in plant development.

Understanding the genetic control of leaf patterning and growth is a central topic in plant biology with important applications in agriculture.  Maize leaves are composed of the blade with supporting midrib, the hinge-like auricle and accompanying ligule (i.e., ligular region), and the stem-grasping sheath.  Variation in blade, auricle and/or sheath morphology can dramatically impact leaf architecture, which can influence canopy structure and planting density.  In a collaborative effort to understand when and how the maize blade/sheath boundary is established, we used laser microdissection followed by RNA sequencing to discover boundary-like expression profiles.  Profiling contiguous microdomains at the base of early leaf primordia discovered 1,045 differentially expressed genes.  KNOTTED1-LIKE HOMEOBOX (KNOX) genes, which are known key regulators of organ boundary development, were enriched at the base of primordia.  Genetic analysis of additional boundary genes, including KNOX co-expressed ZINC-FINGER HOMEODOMAIN encoding genes, supported co-expression networks that act to prepattern the blade/sheath boundary.  Our work suggests prepatterning of the blade/sheath boundary is initiated at the base of leaf primordia by a KNOX gene network that acts in concert with more distal factors to delineate the boundary at the ligular region.

The phytohormone ethylene is a pivotal stress response signal and a key regulator of plant development and growth.  However, neither the genetic control of ethylene response nor the natural variation that may underlie it are well-understood in cereal crops.  To understand the role of ethylene in maize development, I am investigating the function of genes involved in ethylene signaling and natural variation of ethylene response.  My seminar will also introduce this ongoing work.