mimics heat and drought stress and encodes a protoxylem-specific transcription factor in maize.

Maintaining sufficient water transport during flowering is essential for proper organ growth, fertilization, and yield. Water deficits that coincide with flowering result in leaf wilting, necrosis, tassel browning, and sterility, a stress condition known as "tassel blasting." We identified a mutant, (), that mimics tassel blasting and drought stress and reveals the genetic mechanisms underlying these processes. The phenotype is evident only after the floral transition, and the mutants have difficulty moving water as shown by dye uptake and movement assays. These defects are correlated with reduced protoxylem vessel thickness that indirectly affects metaxylem cell wall integrity and function in the mutant. is caused by an transposon insertion into the coding region of a unique transcription factor within the clade of NUT1 localizes to the developing protoxylem of root, stem, and leaf sheath, but not metaxylem, and its expression is induced by flowering. NUT1 downstream target genes function in cell wall biosynthesis, apoptosis, and maintenance of xylem cell wall thickness and strength. These results show that maintaining protoxylem vessel integrity during periods of high water movement requires the expression of specialized, dynamically regulated transcription factors within the vasculature.