Biology subjects

Pimenta Lange, M. J.

Publications and source records attributed to Pimenta Lange, M. J..

3 recordsLinked to original sources

bioRxiv2026

Repeated UV-C exposure alters gibberellin homeostasis and inhibits growth in Arabidopsis thaliana

Ultraviolet-C (UV-C) radiation can be highly damaging to plants, yet its effects on gibberellin (GA) homeostasis are not well understood. In this study, we show that short daily UV-C pulse treatments (12 s, 1,200 J m-2) applied for seven days reduce plant height and delay flowering in Arabidopsis thaliana. Endogenous levels of the GA biosynthesis precursors GA12, GA53, GA15, and GA24, the bioactive GA4, and the GA catabolites GA34 and GA110 are all lower in UV-C treated plants than in untreated controls. These changes were accompanied by lower transcript levels of the GA biosynthesis genes KS, GA13ox1, GA20ox1, and GA3ox1, together with opposing changes in the expression of GA2ox genes. Exogenous GA4 restores growth in UV-C-treated plants, suggesting that reduced GA availability contributes to UV-C-induced growth inhibition. Consistent with this finding, the GA-signalling mutant gdella and the GA-biosynthesis mutants kao1 and kao2 show strongly reduced UV-C responses. Together, these findings highlight the importance of GA metabolism and signalling in the developmental response to repeated UV-C exposure, and suggest that exposure regimen influences the dynamics of UV-C-induced hormonal responses.

plant biology↗

bioRxiv2026

A single UV-C pulse modulates Gibberellin homeostasis and Plant Development in Arabidopsis

Under natural growth conditions, plants are not usually exposed to the high-energy ultraviolet C range (UV-C, 100-280 nm) of the solar spectrum, as this is absorbed by the ozone layer. However, low doses of UV-C radiation can trigger stress responses in plants. Nevertheless, it is not yet fully understood how UV-C light affects plant development at the hormonal level. Here we show that a single one-min UV-C light pulse (20 W/m2) alters gibberellin (GA) homeostasis in Arabidopsis in two phases: initially, the level of GA12 - a key precursor of the final part of gibberellin biosynthesis - is reduced. Consistent with this, the transcript levels of the CPS, KS and KAO2 genes, which encode enzymes involved in the initial parts of gibberellin biosynthesis, decrease. The level of the plant hormone GA4 also decreases initially, probably due to the reduced GA12 precursor levels. However, in a second phase, the endogenous GA4 levels rise in UV-C treated plants relative to control plants. This increase leads to an early onset of flowering, as well as increased growth and fertility, in UV-C-treated Arabidopsis plants. The GA signalling mutant gdella does not exibit wild-type phenotypic responses to UV-C treatment, indicating that GA signalling is essential for the UV-C response. To further narrow down the responsible steps in the GA-signalling pathway, we tested the kao1 and kao2 mutants, which are both impaired in early gibberellin biosynthesis. Neither mutant displays phenotypic responses to the UV-C treatment, indicating that both genes are required for mediating the UV-C response. In contrast, the quintuple 2-oxidase mutant C19--2oxqM exhibits responses to UV-C treatment similar to the wild-type, suggesting that the five catabolic 2-oxidases that act on C19-GAs play a negligible role in regulation GA-hormone levels for growth and development in this case. HighlightUV-C pulse triggers biphasic gibberellin dynamics, delaying early development but ultimately enhancing growth and fertility in Arabidopsis thaliana.

plant biology↗

bioRxiv2022

GAS2 encodes a 2-oxoglutarate dependent dioxygenase involved in ABA catabolism

Liu et al.1 recently reported the characterization of Arabidopsis thaliana GAS2 (Gain of Function in ABA-modulated Seed Germination 2), which was described as an enzyme that catalyzes the stereospecific hydration of GA12 to produce GA12 16, 17-dihydro-16-ol (DHGA12). However, as previously reported2, we did not find conversion of [17-14C]-labeled or [1-,7-,12-,18-14C4]-labeled GA12 by GAS2. Furthermore, the authors1 state the isolation of endogenous DHGA12 from dry Arabidopsis seeds, which we cannot confirm by our attempts to isolate this compound from 0.5 g dry Arabidopsis Col-0 seeds (data not shown). Instead, we present here data showing that the recombinant GAS2 enzyme is able to catabolize abscisic acid (ABA) to phaseic acid (PA) and further to a second product, putative 8-carboxy-ABA (Fig. 1a). O_FIG O_LINKSMALLFIG WIDTH=141 HEIGHT=200 SRC="FIGDIR/small/516706v1_fig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@18fe917org.highwire.dtl.DTLVardef@11006a1org.highwire.dtl.DTLVardef@1235c94org.highwire.dtl.DTLVardef@930b98_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFig. 1.C_FLOATNO GAS2 is an ABA catabolizing oxidase. (a) The proposed ABA catabolic pathway catalyzed by GAS2. (b) Metabolism of d6-ABA incubated with 70 l cell-lysate of recombinant ATGA2ox1 and cofactors (negative control, upper lane). Metabolism of d6-ABA incubated with different volumes of cell-lysates containing recombinant GAS2 and cofactors as described in Methods. Chromatograms of characteristic single ions are shown in the first row for ABA (194 Da), in the middle row for PA (125 DA), and in the right row for compound A (194 Da). Products that were identified on the basis of their mass spectra of the methyl ester derivatives are labelled in red. (c) Top lane: Representative mass spectra of the d6-ABA substrate (KRI = 2087), and of its incubation products, PA (KRI = 2141) and compound A (KRI = 2197), by recombinant GAS2 enzyme. Bottom lane: Mass spectra of unlabeled PA substrate (KRI = 2146), and of the incubation product, compound A (KRI = 2201), by recombinant GAS2 enzyme. C_FIG

plant biology↗