Analyses of leaf morphological changes and expressed genes related to water shortage of Fagus orientalis populations in a drought gradient

Abstract

Climate change models predict an increase in mean annual temperature, a decrease in precipitation and consequently a scarcity of water resources during the growing season for Iran, including the northern forests of the country. One of the consequences is increased water shortage stress during the summer season. Fagus orientalis Lipsky is one of the most important commercial broad leaf species in the Hyrcanian forests and its potential of phenotypic and genetic adaptation to the climate change is essentially vital. The present research was carried out along two precipitation gradients from very humid to semi-humid conditions on four beech populations. The results of the flexibility of the leaf morphological traits showed that the populations of dryer regions had smaller and more elongated leaves than other populations. Evaluation of the expression of seven candidate genes in response to water shortage showed that the expression of aldehyde dehydrogenase, ascorbate peroxidase, Dehydrin (DHN), early responsive to dehydration, late embryogenesis abundant and Cys/His-Type Zinc-Finger in the eastern population was higher than that in the western population, while a difference in elevation gradient was only observed in the expression of some genes. Therefore, the natural selection pressure in the past evolutionary periods in the westeast gradient seems to be higher than the elevation gradient and has led to greater resistance to drought. Principal component analysis revealed that aldehyde dehydrogenase genes (ALDH), early responsive to dehydration (ERD), late embryogenesis abundant (LEA) and DHN are the most effective genes responding to water shortage stress for Oriental beech in the Hyrcanian forests. Keywords: drought gradient, Fagus orientalis, gene expression, leaf morphology