Project description:Autophagy, involved in protein degradation and amino acid recycling, plays a key role in plant development and stress responses. However, the relationship between autophagy and phytohormones is unclear. We used diverse methods, including CRISPR/Cas9, UPLC-MS/MS, chromatin immunoprecipitation, electrophoretic mobility shift assays, and dual-luciferase assays to explore the molecular mechanism of strigolactones in regulating autophagy and the degradation of ubiquitinated proteins under cold stress in tomato. We show that cold stress induced the accumulation of ubiquitinated proteins. Mutants deficient in strigolactone biosynthesis were more sensitive to cold stress with a higher accumulation of ubiquitinated proteins, while treatment with the synthetic strigolactone analog GR245DS enhanced cold tolerance in tomato, with a higher accumulation of autophagosomes and transcripts of autophagy-related genes (ATGs), and a lower accumulation of ubiquitinated proteins. Meanwhile, cold stress induced ELONGATED HYPOCOTYL 5 (HY5) accumulation, which was triggered by strigolactones. HY5 further trans-activated ATG18a promoter, resulting in autophagy formation. Mutation of ATG18a compromised strigolactone-induced cold tolerance, followed by a decreased formation of autophagosomes and an increased accumulation of ubiquitinated proteins. These findings reveal that strigolactones positively regulate autophagy in an HY5-dependent manner and promote the degradation of ubiquitinated proteins under cold conditions in tomato.
Project description:Plants must properly integrate noisy temperature signals to monitor seasonal progression. However, the global regulatory landscape underlying cold acclimation and adaption of plants to noisy and fluctuating natural cold conditions remain poorly investigated. Here, we perform a deep-coverage RNA-seq to investigate the transcriptome dynamics of Arabidopsis thaliana plants grown over weeks of a fluctuating temperature regime, mimicking natural cold conditions of autumn and early winter, or grown using an average daily temperature profile without any temperature fluctuations. We show that progressive cold induces three main patterns of transcriptional response: dynamic-, cooling- and chilling-responsive gene activation. Progressive cold induces a complex network of regulators that could be responsible for the regulation of distinct transcriptional programs. Surprisingly, we find only small differences in cold-responsive gene expression between average and fluctuating conditions. We also highlight that temperature before time is the principal driver of cold transcriptional reprogramming. By combining RNA-seq and ATAC-seq data, we observe that the induction of cold-responsive genes is associated with an increase of promoter accessibility whereas down-regulated genes do not lose accessibility, allowing plants to rapidly reactivate transcription after the return of favourable conditions.
Project description:The epigenetic silencing of the Arabidopsis floral repressor gene FLOWERING LOCUS C (FLC) is induced by a prolonged period of cold and promotes the developmental transition to flowering post-cold. FLC silencing requires the function of VRN1, a non-sequence-specific DNA binding protein. Here, we used Arabidopsis seedlings growing at ambient temperature carrying a FLAG-tagged VRN1 under its endogenous promoter in the vrn1FRI mutant background. We performed FLAG immunoprecipitation followed by mass spectrometry (IP-MS) on crosslinked tissue. The proteomics analysis revealed several proteins that support the role of VRN1 as a chromatin regulator. The identified proteins associated with VRN1 in vivo also support its contribution to gene silencing.
Project description:Transcription regulation requires many protein interactions on chromatin, and only a subset of transcription factors have well-defined activation or repression domains. The Arabidopsis transcription factor HY5 controls critical growth-related gene expression programs during plant development, but it’s primary activity in regulating transcription remains unclear. To address this question, we generated constitutive repressor and activator HY5 fusion proteins to direct the expression of HY5 target genes. We used RNA-seq, ChIP-seq, and multiple phenotypes to demonstrate that HY5 depends on accessory factors to promote transcription and identify high confidence direct targets of HY5. We suggest that this strategy can be used broadly to define the transcription regulation activity and direct targets of transcription factors. Interestingly, this approach also revealed a mechanism by which HY5 promotes the accumulation of its own negative regulators. We show that HY5 directly regulates components of the COP1 E3-ubiquitin ligase complex, and by uncoupling this feedback loop we can induce partial de-etiolation in the dark. This provides a system by which plants can quickly repress growth upon light exposure. Lastly, we show that modulating this system can generate significant phenotypic diversity and provide proof of concept that these fusion proteins can modulate growth in tomato, opening a novel path toward selecting desirable traits in crop species.
Project description:The epigenetic silencing of the Arabidopsis floral repressor gene FLOWERING LOCUS C (FLC) is induced by a prolonged period of cold and promotes the developmental transition to flowering post-cold. FLC silencing requires the function of VRN1, a non-sequence-specific DNA binding protein. Here, we used Arabidopsis seedlings subjected to cold, carrying a FLAG-tagged VRN1 under its endogenous promoter in the vrn1FRI mutant background. We performed FLAG immunoprecipitation followed by mass spectrometry (IP-MS) on crosslinked tissue. The proteomics analysis revealed several proteins that support the role of VRN1 as a chromatin regulator. The identified proteins associated with VRN1 in vivo also support its contribution to gene silencing.