Physiologic responses and gene diversity indicate olive alternative oxidase as a potential source for markers involved in efficient adventitious root induction

Abstract

Olive (Olea europaea L.) trees are mainly propagated by adventitious rooting of semi-hardwood cuttings. However, efficient commercial propagation of valuable olive tree cultivars or landraces by semi-hardwood cuttings can often be restricted by a low rooting capacity. We hypothesize that root induction is a plant cell reaction linked to oxidative stress and that activity of stress-induced alternative oxidase (AOX) is importantly involved in adventitious rooting. To identify AOX as a source for potential functional marker sequences that may assist tree breeding, genetic variability has to be demonstrated that can affect gene regulation. The paper presents an applied, multidisciplinary research approach demonstrating first indications of an important relationship between AOX activity and differential adventitious rooting in semi-hardwood cuttings. Root induction in the easy-to-root Portuguese cultivar 'Cobrançosa' could be significantly reduced by treatment with salicyl-hydroxamic acid, an inhibitor of AOX activity. On the contrary, treatment with H2O2 or pyruvate, both known to induce AOX activity, increased the degree of rooting. Recently, identification of several O. europaea (Oe) AOX gene sequences has been reported from our group. Here we present for the first time partial sequences of OeAOX2. To search for polymorphisms inside of OeAOX genes, partial OeAOX2 sequences from the cultivars 'Galega vulgar', 'Cobrançosa' and 'Picual' were cloned from genomic DNA and cDNA, including exon, intron and 3'-untranslated regions (3'-UTRs) sequences. The data revealed polymorphic sites in several regions of OeAOX2. The 3'-UTR was the most important source for polymorphisms showing 5.7% of variability. Variability in the exon region accounted 3.4 and 2% in the intron. Further, analysis performed at the cDNA from microshoots of 'Galega vulgar' revealed transcript length variation for the 3'-UTR of OeAOX2 ranging between 76 and 301 bp. The identified polymorphisms and 3'-UTR length variation can be explored in future studies for effects on gene regulation and a potential linkage to olive rooting phenotypes in view of marker-assisted plant selection.

Development of a large set of SNP markers for assessing phylogenetic relationships between the olive cultivars composing the Israeli olive germplasm collection

“…Until a recently published study (Kaya et al 2013), only a small number of SNP loci had been identified in olives (Hakim et al 2010;Macedo et al 2009;Muleo et al 2009;Reale et al 2006). Kaya's study used deep sequencing for the identification of 2987 SNPs in olives (Kaya et al 2013 Fig.…”

“…Various DNA markers have been used in these studies including restriction fragment length polymorphism (RFLP) (Bazakos et al 2012;Besnard and Berville 2002), amplified fragment length polymorphism (AFLP) (Albertini et al 2011;Angiolillo et al 1999;Baldoni et al 2006), random amplified polymorphic DNA (RAPD) (Awan et al 2011;Leva and Petruccelli 2012;Parra-Lobato et al 2012), sequence-characterized amplified regions (SCAR) (Marieschi et al 2011), DaRT (Domínguez-García et al 2012, SSR (Beghe et al 2011;Biton et al 2012;Corrado et al 2011;Delgado-Martinez et al 2012;Ercisli et al 2011;Rehman et al 2012;Rotondi et al 2011) and single nucleotide polymorphism (SNP) Hakim et al 2010;Macedo et al 2009;Muleo et al 2009;Reale et al 2006).…”

When stress and development go hand in hand: main hormonal controls of adventitious rooting in cuttings

“…Moreover, a complex interaction between AOX and H 2 O 2 signaling is apparent. Application of H 2 O 2 could replace added auxin as a rooting agent in olive cuttings (Santos-Macedo et al, 2009) and the presence of an AOX inhibitor, salicylhydroxamic acid (SHAM), reduced rooting even in presence of exogenous auxin (Santos-Macedo et al, 2012). …”

In VitroCulture Conditions andOeARFandOeH3Expressions Modulate Adventitious Root Formation fromOleaster(Olea europaeaL. subsp.europaeavar.sylvestris) Cuttings

“…Taking these data into account, we tested a short IBA pulse, followed by two different IBA concentrations and the rooting efficiency was 70% and 90%, respectively, compared to the rate around 20% or below which characterizes many olive cultivars [23]. Unexpectedly, adventitious rooting was achieved also on medium devoid of IBA and the efficiency was similar to that obtained at the lowest IBA concentration.…”