New Paper from George Chuck's Group


When water deficits coincide with flowering in maize they result in severe developmental consequences such as leaf wilting, tassel browning, and sterility, a condition known as “tassel blasting.” Due to global warming, tassel blasting is becoming a major problem that can greatly reduce yields. Necrotic upper tips1 (nut1) is a transcription factor that mimics tassel blasting when mutated. We show that NUT1 protein localizes to the developing protoxylem where it activates genes necessary for reinforcing the secondary cell wall, and thus enables these cells to withstand the high negative pressures required for long-distance water movement. Thus, nut1 or its targets may be promising breeding targets to help maize resist the effects of rising temperatures in the future.


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, necrotic upper tips1 (nut1), that mimics tassel blasting and drought stress and reveals the genetic mechanisms underlying these processes. The nut1 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. nut1 is caused by an Ac transposon insertion into the coding region of a unique NAC transcription factor within the VND clade of Arabidopsis. 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.