Biology subjects

Zacharaki, V.

Publications and source records attributed to Zacharaki, V..

5 recordsLinked to original sources

bioRxiv2025

Two long non-coding RNAs, SVALKA and SVALNA, regulate CBF1 and CBF3 via multiple mechanisms

Long non-coding RNAs (lncRNAs) are emerging as key regulatory players of coding gene expression in eukaryotes. Here, we investigate the roles of the lncRNAs SVALKA (SVK) and SVALNA (SVN) in regulating CBF1 and CBF3 gene expression in Arabidopsis under cold stress conditions. We used Native Elongation Transcript Sequencing, CRISPR-Cas9 deletion strategies, and RT-qPCR to analyze the transcriptional dynamics and regulatory mechanisms of SVK and SVN. Our results demonstrate that SVK functions as a cis- and trans-acting lncRNA, regulating both CBF1 and CBF3 through RNAPII collision and chromatin remodeling, while SVN serves a cis role by negatively regulating CBF3 via a RNAPII collision mechanism. We identified isoforms of SVK, originating from distinct transcription start sites and undergo alternative splicing to adapt structural stability, crucial for their regulatory functions. This study elucidates the complex interplay of lncRNAs in gene regulation, highlighting their essential roles in modulating responses to environmental stresses. Our findings contribute to a deeper understanding of the mechanisms underlying lncRNA functionality and their significance in gene regulatory networks in eukaryotes.

plant biology↗

bioRxiv2024

FLOWERING LOCUS C integrates carbon and nitrogen signaling for the proper timing of flowering in Arabidopsis

The timing of flowering in plants is modulated by both carbon (C) and nitrogen (N) signaling pathways. In a previous study, we established a pivotal role of the sucrose-signaling trehalose 6-phosphate pathway in regulating flowering under N-limited short-day conditions. In this work, we expand on our finding that wild-type plants grown under N-limited short days require an active trehalose 6-phosphate pathway to be able to flower. Both wild-type plants grown under N-limited conditions and knock-down plants of TREHALOSE PHOSPHATE SYNTHASE1 induce FLOWERING LOCUS C expression, a well-known floral repressor associated with the vernalization response. When exposed to an extended period of cold, a mutant of FLOWERING LOCUS C fails to respond to N availability, and flowers at the same time under N-limited and full-nutrition conditions. Our data suggest that SUCROSE NON-FERMENTING 1 RELATED KINASE 1-dependent trehalose 6-phosphate-mediated C signaling and a novel mechanism downstream of N signaling likely involving NIN-LIKE PROTEIN 7 impact the expression of FLOWERING LOCUS C. Collectively, our data underscore the existence of a multi-factor regulatory system in which both C and N signaling pathways jointly govern the regulation of flowering in plants.

plant biology↗

bioRxiv2024

Mutations in HUA2 restore flowering in the Arabidopsis trehalose 6-phosphate synthase1 (tps1) mutant

Plant growth and development are regulated by many factors, including carbohydrate availability and signaling. Trehalose 6-phosphate (T6P), which is synthesized by TREHALOSE-6-PHOSPHATE SYNTHASE 1 (TPS1), is positively correlated with and functions as a signal that informs the cell about the carbohydrate status. Mutations in TPS1 negatively affect the growth and development of Arabidopsis thaliana and complete loss-of-function alleles are embryo lethal, which can be overcome using inducible expression of TPS1 (GVG::TPS1) during embryogenesis. Using EMS mutagenesis in combination with genome re-sequencing we have identified several alleles in the floral regulator HUA2 that restore flowering and embryogenesis in tps1-2 GVG::TPS1. Genetic analyses using a HUA2 T-DNA insertion allele, hua2-4, confirmed this finding. RNA-seq analyses demonstrated that hua2-4 has widespread effects on the tps1-2 GVG::TPS1 transcriptome, including key genes and pathways involved in regulating flowering. Higher order mutants combining tps1-2 GVG::TPS1 and hua2-4 with alleles in the key flowering time regulators FLOWERING LOCUS T (FT), SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), and FLOWERING LOCUS C (FLC) were constructed to analyze the role of HUA2 during floral transition in tps1-2 in more detail. Taken together, our findings demonstrate that loss of HUA2 can restore flowering and embryogenesis in tps1-2 GVG::TPS1 in part through activation of FT, with contributions of the upstream regulators SOC1 and FLC. Interestingly, we found that mutation of FLC is sufficient to induce flowering in tps1-2 GVG::TPS1. Furthermore, we observed that mutations in HUA2 modulate carbohydrate signaling and that this regulation might contribute to flowering in hua2-4 tps1-2 GVG::TPS1.

plant biology↗

bioRxiv2023

Temperature-dependent regulation of Arabidopsis thaliana growth and development by LSM7

Temperature affects plant growth by modulating the expression of genes and subsequent processing of RNAs that govern essential physiological processes. Here, we show that Arabidopsis thaliana Sm-like7 (LSM7), a core component of the splicing and decapping machinery, is indispensable for embryogenesis and development. Hypomorphic lsm7-2 mutants display severe developmental defects that are exacerbated by high temperatures. Transcriptome analysis verified LSM7s extensive role in gene regulation. In particular, we found that the key regulator of thermomorphogenesis, PHYTOCHROME INTERACTING FACTOR 4 (PIF4), and auxin-related genes, including SMALL AUXIN UP-REGULATED (SAUR) genes, are misregulated in lsm7-2. Auxin metabolic profiling confirmed that auxin homeostasis was disturbed in lsm7-2. Importantly, overexpression of the auxin-responsive SAUR19 gene partially restored thermomorphogenesis defects in lsm7-2 under high ambient temperature. Taken together, our research provides mechanistic insights into the interplay between RNA processing, hormone homeostasis, and the response to temperature regulation in plants and elucidates LSM7s essential function in plant temperature acclimation and resilience. Significance StatementGiven their sessile nature, plants cannot escape adverse environmental conditions such as cold or heat. Instead, they continuously adjust their gene expression and RNA processing to regulate growth and physiology in response to their surroundings. In this study, we investigated the role of the core RNA processing factor LSM7 in temperature acclimation in Arabidopsis thaliana. We found that LSM7 knockdown mutants were impaired in thermomorphogenesis and, as a result, were hypersensitive to elevated temperatures. At the molecular level, we demonstrated that this temperature sensitivity was caused by the misregulation of key regulators of thermomorphogenesis, including PIF4, auxin homeostasis and signaling, and SAUR genes. Our findings provide valuable insights into the role of RNA processing in plant temperature acclimation.

plant biology↗

bioRxiv2020

Widespread premature transcription termination of Arabidopsis thaliana NLR genes by the spen protein FPA

Genes involved in disease resistance are some of the fastest evolving and most diverse components of genomes. Large numbers of nucleotide-binding, leucine-rich repeat receptor (NLR) genes are found in plant genomes and are required for disease resistance. However, NLRs can trigger autoimmunity, disrupt beneficial microbiota or reduce fitness. It is therefore crucial to understand how NLRs are controlled. Here we show that the RNA-binding protein FPA mediates widespread premature cleavage and polyadenylation of NLR transcripts, thereby controlling their functional expression and impacting immunity. Using long-read Nanopore direct RNA sequencing, we resolved the complexity of NLR transcript processing and gene annotation. Our results uncover a co-transcriptional layer of NLR control with implications for understanding the regulatory and evolutionary dynamics of NLRs in the immune responses of plants.

molecular biology↗