NUT1-Exo70A1 Regulates Xylem Vessel Development and Influences Water Use Efficiency in Maize

Efficient water uptake and transport through xylem vessels are essential for plant growth and development. The patterned secondary cell wall (SCW) structure of xylem vessels provides robust mechanical support to withstand the strong negative pressure generated by transpiration and facilitates long-distance water transport. However, the key factors governing SCW patterning in xylem vessels and their potential for enhancing water use efficiency (WUE) remain undetermined. Here, we report the identification of a recessive maize (Zea mays) mutant drought-sensitive 1 (ds1), which is highly susceptible to water deficit. ds1 defects in SCW patterning and xylem vessel differentiation, and exhibits significantly reduced hydraulic conductivity. DS1 is the ortholog of Arabidopsis Exo70A1 and is regulated by the NAC transcription factor NECROTIC UPPER TIPS1 (NUT1) in vascular tissues. Overexpressing Exo70A1 enhanced hydraulic conductivity and consequently boosted biomass and grain yield under both well-watered and drought conditions. Thus, the NUT1-Exo70A1 module represents a promising genetic target for improving WUE in crops.