Changes in GA 20‐oxidase gene expression strongly affect stem length, tuber induction and tuber yield of potato plants

Abstract

Gene StGA20ox1 encoding potato GA 20-oxidase is expressed to relatively high levels in leaves and regulated by daylength. To investigate whether this gene is involved in photoperiodic regulation of tuber formation, we have obtained transgenic potato plants expressing sense and antisense copies of the StGA20ox1 cDNA. Over-expression of this cDNA resulted in taller plants that required a longer duration of a short day photoperiod (SD) to tuberize. Tubers from these plants had a decreased time of dormancy and developed sprouts with elongated internodes. Plants expressing antisense copies of the StGA20ox1 cDNA had shorter stems, a decreased length of the internodes and tuberized earlier than control plants, showing increased tuber yields. Antisense inhibition of this gene had no visible effect on the time of dormancy of the tubers, although at the end of dormancy these formed sprouts with shortened internodes. Decreased levels of endogenous GA20 and GA1 were detected in the apex and first leaves of the antisense lines. These results demonstrate the involvement of the GA 20-oxidase activity encoded by StGA20ox1 in the control of stem elongation and in tuber induction but not in tuber dormancy, indicating that the latter may be regulated by another member of the gene family.

Regulation of potato tuber sprouting

“…Transgenic lines with ectopic expression of the GA biosynthetic gene GA20-oxidase from either potato or Arabidopsis thaliana exhibited a shortened time of dormancy and developed elongated sprouts, confirming the growth promoting activity of GA (Carrera et al 2000;Hartmann et al 2011). In contrast, modified expression of endogenous GA2-oxidase gene, whose product is involved in inactivation of bioactive GAs and their precursors (Hedden 2001), did not affect the length of the dormancy period in transgenic potato tubers (Kloosterman et al 2007).…”

“…Tuber development is regulated by an interplay between endogenous and environmental signals and is orchestrated by coordinated transcriptional and metabolic changes (Kloosterman et al 2005(Kloosterman et al , 2008Ferreira et al 2010). The process was shown to be controlled by phytohormones including gibberellins (GAs), auxin and strigolactones (SLs) (Carrera et al 2000;Kloosterman et al 2007;Roumeliotis et al 2012;Pasare et al 2013). However, an important trigger comes from environmental cues.…”

The endogenous plant hormones and ratios regulate sugar and dry matter accumulation in Jerusalem artichoke in salt-soil

“…Xu et al (1998) assumed that the endogenous GA 1 content was high during stolon elongation and decreased when stolons started to swell under tuber-inducing conditions, whereas it remained high under noninducing conditions. Carrera et al (2000) elevated the GA 3 oxidase overexpression led to a longer duration of short-day photoperiods to form tubers by transgenic potato plants, whereas antisense inhibition of this enzyme resulted in tuberization happening earlier than in control plants.…”

Cloning and Overproduction of Gibberellin 3-Oxidase in Hybrid Aspen Trees. Effects on Gibberellin Homeostasis and Development

“…Accelerated growth as a response to ectopic GA20ox expression and increased levels of GA growth regulator have also been observed in Arabidopsis (Huang et al, 1998;Coles et al, 1999), potato (Solanum tuberosum; Carrera et al, 2000), and tobacco (Nicotiana tabacum; Vidal et al, 2001), implying that this enzyme has a limiting role in regulating the production of bioactive GAs. In contrast, when the genes coding for ent-copalyl diphosphate synthase and ent-kaurene synthase, which are involved in early stages of GA biosynthesis, are overexpressed in Arabidopsis, no significantly increased levels of bioactive GA are observed (Fleet et al, 2003).…”