Regulation of Transcript Levels of a Potato Gibberellin 20-Oxidase Gene by Light and Phytochrome B

Jackson, Stephen D.; James, Pat E.; Carrera, Esther; Prat, Salomé; Thomas, Brian

doi:10.1104/pp.124.1.423

Cited by 55 publications

(22 citation statements)

References 32 publications

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“…In Sorghum bicolor, phytochrome B seems to control the daily regulation of GA 20 biosynthesis (Foster and Morgan, 1995). Also, in potato, phytochrome B is involved in the regulation of transcript levels of one GA20-oxidase gene (Jackson et al, 2000). A rhythm of PsGA20ox1 steady-state expression has also been reported in pea leaves with higher steady-state expression in light than in dark (Garcia-Martinez and Gil, 2002).…”

Section: Discussionmentioning

confidence: 99%

Thermoperiodic Stem Elongation Involves Transcriptional Regulation of Gibberellin Deactivation in Pea

et al. 2005

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The physiological basis of thermoperiodic stem elongation is as yet poorly understood. Thermoperiodic control of gibberellin (GA) metabolism has been suggested as an underlying mechanism. We have investigated the influence of different day and night temperature combinations on GA levels, and diurnal steady-state expression of genes involved in GA biosynthesis (LS, LH, NA, PSGA20ox1, and PsGA3ox1) and GA deactivation (PsGA2ox1 and PsGA2ox2), and related this to diurnal stem elongation in pea (Pisum sativum L. cv Torsdag). The plants were grown under a 12-h light period with an average temperature of 17°C. A day temperature/night temperature combination of 13°C/21°C reduced stem elongation after 12 d by 30% as compared to 21°C/13°C. This was correlated with a 55% reduction of GA 1 . Although plant height correlated with GA 1 content, there was no correlation between diurnal growth rhythms and GA 1 content. NA, PsGA20ox1, and PsGA2ox2 showed diurnal rhythms of expression. PsGA2ox2 was up-regulated in 13°C/21°C (compared to 21°C/13°C), at certain time points, by up to 19-fold. Relative to PsGA2ox2, the expression of LS, LH, NA, PSGA20ox1, PsGA3ox1, and PsGA2ox1 was not or only slightly affected by the different temperature treatments. The sln mutant having a nonfunctional PsGA2ox1 gene product showed the same relative stem elongation response to temperature as the wild type. This supports the importance of PsGA2ox2 in mediating thermoperiodic stem elongation responses in pea. We present evidence for an important role of GA catabolism in thermoperiodic effect on stem elongation and conclude that PsGA2ox2 is the main mediator of this effect in pea.The ability of plants to discriminate between temperature during the day and night in their response to flowering, fruiting, and growth is referred to as thermoperiodism (Went, 1944). Erwin et al. (1989) showed that the effects of diurnal temperature alternation on stem length in Lilium longiflorum could best be described by the mathematical difference (DIF) between day temperature (DT) and night temperature (NT). Stem elongation thus increases with an increase in DIF, from a negative to a positive value. Stem elongation in many species is affected by the relationship between DT and NT, and the DIF concept is widely used for growth control in production of ornamental plants propagated in a greenhouse (Erwin and Heins, 1995;Myster and Moe, 1995;Moe and Heins, 2000). A negative DIF treatment (low DT and high NT) is a tool to produce compact flower plants and vegetable seedlings with short internodes without a delay in production time. Also, negative DIF treatments have largely replaced the use of chemical growth retardants in a number of commercial cultures.Thus, the use of such temperature regimes has substantial practical and economic implications in addition to representing an environmentally more sustainable method than chemical growth control. However, very little is known about the mechanisms underlying the thermoperiodic responses in plants. Such knowledge will be of gr...

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Section: Discussionmentioning

confidence: 99%

Thermoperiodic Stem Elongation Involves Transcriptional Regulation of Gibberellin Deactivation in Pea

et al. 2005

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“…Remarkably, most lightresponsive genes of GA synthesis were also found to be under wavelength-or photoreceptor-specific control. In Arabidopsis, lettuce (Lactuca sativa), and pea (Pisum sativum), light was shown to regulate the expression of GA 3b-hydroxylase and GA 20-oxidase isoforms via either phytochrome-dependent or -independent mechanisms (Toyomasu et al, 1998;Yamaguchi et al, 1998;Ait-Ali et al, 1999;Jackson et al, 2000).…”

Section: Discussionmentioning

confidence: 99%

“…The toc1-3 mutation was shown to elevate the activity of GA5 that encodes a GA 20-oxidase (Blázquez et al, 2002). In potato (Solanum tuberosum), the complex diurnal profiles of StGA20ox1 and StGA20ox2 expression (Carrera et al, 1999;Jackson et al, 2000) suggest the involvement of circadian regulation. In line with the observed activity changes of GA-biosynthetic genes, the accumulation of bioactive GAs was also found to follow diurnal rhythmicity (Foster and Morgan, 1995).…”

Section: Discussionmentioning

confidence: 99%

Diurnal Regulation of the Brassinosteroid-Biosynthetic CPD Gene in Arabidopsis

et al. 2006

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Plant steroid hormones, brassinosteroids (BRs), are essential for normal photomorphogenesis. However, the mechanism by which light controls physiological functions via BRs is not well understood. Using transgenic plants carrying promoter-luciferase reporter gene fusions, we show that in Arabidopsis (Arabidopsis thaliana) the BR-biosynthetic CPD and CYP85A2 genes are under diurnal regulation. The complex diurnal expression profile of CPD is determined by dual, light-dependent, and circadian control. The severely decreased expression level of CPD in phytochrome-deficient background and the red light-specific induction in wildtype plants suggest that light regulation of CPD is primarily mediated by phytochrome signaling. The diurnal rhythmicity of CPD expression is maintained in brassinosteroid insensitive 1 transgenic seedlings, indicating that its transcriptional control is independent of hormonal feedback regulation. Diurnal changes in the expression of CPD and CYP85A2 are accompanied by changes of the endogenous BR content during the day, leading to brassinolide accumulation at the middle of the light phase. We also show that CPD expression is repressed in extended darkness in a BR feedback-dependent manner. In the dark the level of the bioactive hormone did not increase; therefore, our data strongly suggest that light also influences the sensitivity of plants to BRs.

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“…However, the mechanism by which PHYB controls photoperiodic tuberization is unknown. Although it has been shown that PHYB affects the mRNA levels of a gibberellin-20-oxidase (GA20ox1), a key enzyme in gibberellin biosynthesis that affects tuberization, the alteration of GA20ox1 transcript and GA 1 levels in anti-PHYB plants is not consistent with their tuberization phenotype Jackson et al, 2000;Martínez-García et al, 2002). Therefore, how PHYB negatively regulates tuberization has not been elucidated.…”

Section: Introductionmentioning

confidence: 99%

Graft-transmissible induction of potato tuberization by the microRNA miR172

et al. 2009

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The photoreceptor phytochrome B (PHYB) and the homeodomain protein BEL5 are involved in the response of potato tuber induction to the photoperiod. However, whether they act in the same tuberization pathway is unknown. Here we show the effect of a microRNA, miR172, on this developmental event. miR172 levels are higher under tuber-inducing short days than under noninductive long days and are upregulated in stolons at the onset of tuberization. Overexpression of this microRNA in potato promotes flowering, accelerates tuberization under moderately inductive photoperiods and triggers tuber formation under long days. In plants with a reduced abundance of PHYB, which tuberize under long days, both BEL5 mRNA and miR172 levels are reduced in leaves and increased in stolons. This, together with the presence of miR172 in vascular bundles and the graft transmissibility of its effect on tuberization, indicates that either miR172 might be mobile or it regulates long-distance signals to induce tuberization. Consistent with this, plants overexpressing miR172 show increased levels of BEL5 mRNA, which has been reported to be transmissible through grafts. Furthermore, we identify an APETALA2-like mRNA containing a miR172 binding site, which is downregulated in plants overexpressing miR172 and plants in which PHYB is silenced. Altogether, our results suggest that miR172 probably acts downstream of the tuberization repressor PHYB and upstream of the tuberization promoter BEL5 and allow us to propose a model for the control of tuberization by PHYB, miR172 and BEL5.

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Regulation of Transcript Levels of a Potato Gibberellin 20-Oxidase Gene by Light and Phytochrome B

Cited by 55 publications

References 32 publications

Thermoperiodic Stem Elongation Involves Transcriptional Regulation of Gibberellin Deactivation in Pea

Thermoperiodic Stem Elongation Involves Transcriptional Regulation of Gibberellin Deactivation in Pea

Diurnal Regulation of the Brassinosteroid-Biosynthetic CPD Gene in Arabidopsis

Graft-transmissible induction of potato tuberization by the microRNA miR172

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