Tetraploid Rangpur lime rootstock increases drought tolerance via enhanced constitutive root abscisic acid production

Abstract

Whole-genome duplication, or polyploidy, is common in many plant species and often leads to better adaptation to adverse environmental condition. However, little is known about the physiological and molecular determinants underlying adaptation. We examined the drought tolerance in diploid (2x) and autotetraploid (4x) clones of Rangpur lime (Citrus limonia) rootstocks grafted with 2x Valencia Delta sweet orange (Citrus sinensis) scions, named V/2xRL and V/4xRL, respectively. Physiological experiments to study root-shoot communication associated with gene expression studies in roots and leaves were performed. V/4xRL was much more tolerant to water deficit than V/2xRL. Gene expression analysis in leaves and roots showed that more genes related to the response to water stress were differentially expressed in V/2xRL than in V/4xRL. Prior to the stress, when comparing V/4xRL to V/2xRL, V/4xRL leaves had lower stomatal conductance and greater abscisic acid (ABA) content. In roots, ABA content was higher in V/4xRL and was associated to a greater expression of drought responsive genes, including CsNCED1, a pivotal regulatory gene of ABA biosynthesis. We conclude that tetraploidy modifies the expression of genes in Rangpur lime citrus roots to regulate long-distance ABA signalling and adaptation to stress.

Enhanced Stomatal Conductance by a Spontaneous Arabidopsis Tetraploid, Me-0, Results from Increased Stomatal Size and Greater Stomatal Aperture

“…These differences related to ABA responsiveness seem to affect stomatal aperture between Me-0 and tetraploid Col. del Pozo and Ramirez-Parra (2014) reported that not only tetraploid Arabidopsis Col but also the Landsberg erecta ecotype have smaller stomatal apertures and exhibit differential expression of genes involved in ABA metabolism, compared with their diploid relatives. Tetraploids of another plant species, Rangpur lime, also alter the expression of ABA-related genes and accumulate excessive ABA, thereby decreasing g s (Allario et al, 2011(Allario et al, , 2013. These reports support the possibility that increasing the ploidy level in some ecotypes and plant species changes ABA responsiveness or biosynthesis; however, tetraploidization does not always affect ABA responsiveness or induce an equal effect on ABA responsiveness, as in Me-0 and tetraploid Col.…”

Effect of polyploidization on morphology in two apple (Malus × domestica) genotypes

“…Through gene-dosage and epigenetic effects, together with nuclear enlargement, polyploidy causes genetic changes that result in pronounced phenotypic alterations (Comai 2005;Sun et al 2009;Van Laere et al 2011;Allario et al 2013;Hao et al 2013). Morphological effects commonly associated with polyploidy are bigger flowers, an altered leaf length-to-width ratio and changes in size and density of stomata (Sun et al 2009;Van Laere et al 2011;Trojak-Goluch, Skomra 2013;Tan et al 2015).…”

The “Polyploid Hop”: Shifting Challenges and Opportunities Over the Evolutionary Lifespan of Genome Duplications

“…A major challenge now is to determine the molecular events that bind WGD to this enhanced stress tolerance. It appears that the key tissue to investigate is the root, where salinity and drought tolerance meet potassium homeostasis and ABA signaling (Saleh et al, 2008;Meng et al, 2011;Allario et al, 2013;Chao et al, 2013;Wang et al, 2013;del Pozo and Ramirez-Parra, 2014). Work there promises to reveal mechanistically how WGD has an immediate effect on cellular physiology that is independent of increased genetic diversity.…”