Overexpression of MhYTP2 enhances apple water-use efficiency by activating ABA and ethylene signaling

Abstract

A critical component of crop breeding is the identification of genes involved in improving water-use efficiency (WUE). We characterized MhYTP2, a gene cloned from Malus hupehensis that encodes an RNA-binding protein, to examine its role in WUE. Under both well-watered and drought conditions, overexpression of this gene enhanced WUE in transgenic plants and they accumulated more biomass than untransformed wild-type plants. This increase in WUE was probably due to enhancement of photosynthetic rate and root water uptake, and a reduction in stomatal aperture that resulted from elevated level of ABA and activated ethylene signaling. MhYTP2 was predominantly expressed in apple roots. We noted with interest that the rate of photosynthesis, instantaneous WUE, and root water potential were higher when 35S:MhYTP2 plants were used as rootstocks rather than as scions in our grafting experiments. Our results indicated that MhYTP2 has a more crucial role in the roots than in the aerial parts of the plant, and it implies that this gene can be used for improving WUE by apple rootstocks and, potentially, rootstocks of other graft-suitable crops.