Biology subjects

Lukas, H.

Publications and source records attributed to Lukas, H..

2 recordsLinked to original sources

bioRxiv2025

Non-transcriptional gibberellin DELLA signalling for microtubule dynamics

Plant cell growth is associated with changes in the dynamics and orientation of the microtubule (MT) cytoskeleton. The plant hormone Gibberellic acid (GA), a central regulator of growth also has an impact on MT arrangements, however the causal relationship between these processes and underlying molecular mechanism remain unclear. Here, examining the Arabidopsis thaliana root elongation zone, we show that MT reorientation occurs as a consequence of GA-induced cell elongation and that GA has also a direct effect on the rate of MT polymerization via a non-transcriptional mechanism. Preventing cell elongation blocked GA-induced MT reorganization, whereas GA still promoted elongation in the absence of intact MTs. On the other hand, GA promoted MT dynamics as revealed by the recovery of MTs following depolymerization or photobleaching. Live imaging revealed that GA directly promotes MT polymerization at their plus ends. This GA effect persists even when transcription or translation are inhibited, but still requires the DELLA canonical components of GA signalling and their interactors, the prefoldins (PFDs). Our results support a model where GA-induced DELLA degradation releases in nucleus sequestrated PFDs, enhancing their cytoplasmic function to promote MT polymerization. Hence, GA signalling branches into two mechanistically distinct modules: (i) canonical transcriptional pathway that promotes growth and indirectly drives MT reorientation; and (ii) the non-transcriptional DELLA-PFD axis that directly promotes MT polymerization. Such a dual mechanism enables plants to synchronize growth with cytoskeletal remodelling by coupling rapid, cytoplasmic responses to slower transcriptional programs.

cell biology↗

bioRxiv2018

RppH can faithfully replace TAP to allow cloning of 5’-triphosphate carrying small RNAs

RNA interference was first described in the nematode Caenorhabditis elegans. Ever since, several new endogenous small RNA pathways have been described and characterized to different degrees. Much like plants, but unlike Drosophila and mammals, worms have RNA-dependent RNA Polymerases (RdRPs) that directly synthesize small RNAs using other transcripts as a template. The very prominent secondary small interfering RNAs, also called 22G-RNAs, produced by the RdRPs RRF-1 and EGO-1 in C. elegans, maintain the 5 triphosphate group, stemming from RdRP activity, also after loading into an Argonaute protein. This creates a technical issue, since 5PPP groups decrease cloning efficiency for small RNA sequencing. To increase cloning efficiency of these small RNA species, a common practice in the field is the treatment of RNA samples, prior to library preparation, with Tobacco Acid pyrophosphatase (TAP). Recently, TAP production and supply was discontinued, so an alternative must be devised. We turned to RNA 5 pyrophosphohydrolase (RppH), a commercially available pyrophosphatase isolated from E. coli. Here we directly compare TAP and RppH in their use for small RNA library preparation. We show that RppH-treated samples faithfully recapitulate TAP-treated samples. Specifically, there is enrichment for 22G-RNAs and mapped small RNA reads show no small RNA transcriptome-wide differences between RppH and TAP treatment. We propose that RppH can be used as a small RNA pyrophosphatase to enrich for triphosphorylated small RNA species and show that RppH- and TAP-derived datasets can be used in direct comparison.

molecular biology↗