The maize aquaporin ZmPIP1;6 enhances stomatal opening and CO2- and ABA-induced stomatal closure.

The plasma membrane aquaporin ZmPIP1;6 is expressed in maize stomatal complexes, with higher expression during the day than at night. To elucidate the role of ZmPIP1;6 in gas exchange and stomatal movement, it was expressed in maize (inbred line B104) under the control of the p35S promoter (overexpression) or its native promoter fused with mYFP (monomeric yellow fluorescent protein) cDNA (mYFP-ZmPIP1;6). In stomatal complexes of the mature zone of the leaf, mYFP-ZmPIP1;6 showed higher expression in subsidiary cells than in guard cells, and light and dark treatments influenced its subcellular localization.

Genetic variability of aquaporin expression in maize: From eQTLs to a MITE insertion regulating PIP2;5 expression.

Plant aquaporins are involved in numerous physiological processes, such as cellular homeostasis, tissue hydraulics, transpiration, and nutrient supply, and are key players of the response to environmental cues. While varying expression patterns of aquaporin genes have been described across organs, developmental stages, and stress conditions, the underlying regulation mechanisms remain elusive. Hence, this work aimed to shed light on the expression variability of 4 plasma membrane intrinsic protein (PIP) genes in maize (Zea mays) leaves, and its genetic causes, through expression quantitative trait locus (eQTL) mapping across a 252-hybrid diversity panel.