Biology subjects

Carella, P.

Publications and source records attributed to Carella, P..

8 recordsLinked to original sources

bioRxiv2026

Canonical NLR immune receptor architecture enforces EDS1-dependency onto divergent TIR domains

Toll/interleukin-1 receptor (TIR) enzymes are prominent immune components in diverse organisms across the tree of life. In flowering plants, TIRs are often integrated into nucleotide binding leucine-rich repeat (NLR) receptors whose oligomerization-dependent biochemical activities create second messengers perceived by ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1)-family signaling complexes. TIR-NLRs and TIR proteins are present across the full spectrum of plant evolution, yet EDS1 signaling is a derived trait in seed plants. Here, we examined the functional dependency of diverse plant TIRs on the EDS1 pathway in the angiosperms Nicotiana benthamiana and Nicotiana tabacum. While the isolated TIR domains from non-seed plants generally required EDS1 for immune cell death activation, we also identified TIRs that functioned independent of EDS1. However, chimeric TIR-NLRs incorporating these diverse TIR domains onto the AtWRR4a receptor chassis showed a full reversion to EDS1-dependency. Extending this phenomenon further, we demonstrated that the AtWRR4a architecture enforces EDS1-dependence onto a bacterial TIR domain that is otherwise EDS1-independent. Collectively, our work demonstrates that NLR immune receptor architecture influences TIR-related immunity and provides further context to their ancient acquisition into plant immune systems.

plant biology↗

bioRxiv2025

Stepwise and lineage-specific divergence of a major immune co-chaperone complex in leptosporangiate ferns

Protein-protein interactions are essential for proper cellular function and are often under strong evolutionary pressures to maintain their stability and specificity. In plants, a broadly distributed chaperone complex comprised of the RAR1 (REQUIRED FOR MLA12 RESISTANCE 1) and SGT1 (SUPRESSOR OF THE G2 ALLELE OF SKP1) co-chaperones alongside the HSP90 (HEAT SHOCK PROTEIN90) core chaperone are important for immunity. Despite its importance in flowering plants, a deeper understanding of how this complex evolved remains limited. Here, we examine the molecular evolutionary history of the RAR1-SGT1 interaction across land plants. We identified a lineage-specific divergence of the RAR1-SGT1 binding interface in vascular non-seed ferns, which renders orthologs unable to interact outside of their lineage. Further investigation of interface diversity uncovered a single amino acid residue in RAR1 and three corresponding residues in SGT1 that collectively dictate binding specificity. Ancestral state reconstruction supported stepwise evolution of specificity in SGT1 in leptopsporangiate ferns, which was initiated by a promiscuous intermediate state that widened its capacity to bind RAR1 before subsequent mutations locked in specificity. Our data highlight the broad conservation of the RAR1-SGT1 interface and the coevolutionary dynamics that shaped interface maintenance during lineage-specific diversification.

plant biology↗

bioRxiv2025

Herbaria provide a valuable resource for obtaining informative mRNA

While DNA has built the framework for molecular insights from museum collections, the utility of archival RNA remains largely unexplored. Likely a consequence of the known instability of RNA relative to DNA, this has effectively precluded the use of herbaria for transcriptomics. Here, we challenge the assumption that herbaria cannot be used for transcriptomics by assembling transcriptomes from RNA extracted from herbarium specimens. Through systematic comparison of transcriptomes from fresh-collected, silica-dried, and archival specimens, we demonstrate the suitability of herbarium-derived RNA for transcriptomics. We show the practical applicability of archival mRNA by functionally validating a plant immune receptor synthesized from a specimen collected in 1956. These results contradict the community consensus regarding archival RNA and open the door to subsequent transcriptomic explorations of rare and extinct plant species. Our findings highlight the importance of preserving and utilizing the diversity embedded within herbarium collections.

plant biology↗

bioRxiv2024

Conserved effectors underpin the virulence of liverwort-isolated Pseudomonas in divergent plants

Plant pathogenic Pseudomonas species naturally antagonize a diverse range of flowering plants. While emerging research demonstrates that isolates belonging to the P. syringae species complex colonize diverse hosts, the extent to which these bacteria naturally infect non-flowering plants like the model liverwort Marchantia polymorpha remains unclear. Here, we identify natural associations between Pseudomonas viridiflava and the liverwort Marchantia polymorpha. Pseudomonas bacteria isolated from diseased liverworts in the wild successfully re-infected M. polymorpha in pure culture conditions, producing high in planta bacterial densities and causing prominent tissue maceration. Comparative genomic analysis of Marchantia-associated P. viridiflava identified core virulence machinery like the type-III secretion system (T3SS) and conserved effectors (AvrE and HopM1) that were essential for liverwort infection. Disease assays performed in Nicotiana benthamiana further confirmed that liverwort-associated P. viridiflava infect flowering plants in an effector-dependent manner. Our work highlights P. viridiflava as an effective broad host pathogen that relies on conserved virulence factors to manipulate evolutionarily divergent host plants.

plant biology↗

bioRxiv2024

An environment-responsive SCLA-type GRAS protein controls reproductive strategy in Marchantia polymorpha

By controlling their reproductive strategies, plants strike a balance between generating genetic diversity or maintaining stability, promoting long-term survival in a range of environmental conditions. The liverwort Marchantia polymorpha propagates clonally through vegetative gemmae or via sexually generated spores, but our understanding of the genetic pathways underpinning reproductive decision-making is limited. GRAS transcriptional regulators are highly conserved proteins across land plants, with diverse functionality in stress and development. Here, we discover a central role for the SCLA-type transcription regulator MpGRAS7 in both stress signalling and reproduction in Marchantia. MpGRAS7 is highly expressed in gemma cups and gametangiophores and is activated in response to Far Red (FR) light and abscisic acid (ABA) environmental cues. Genetic dissection further suggests MpGRAS7 is required to maintain gemma dormancy, gemma cup frequency, and FR-induced gametangiophore development. The sequence conservation and expression patterns of MpGRAS7 orthologs in flowering plants hints towards the broader function of SCLA-type GRAS proteins in stress-regulated developmental transitions in plants.

plant biology↗

bioRxiv2024

A Necrotizing Toxin Promotes Pseudomonas syringae Infection Across Evolutionarily Divergent Plant Lineages

The Pseudomonas syringae species complex harbors a diverse range of plant pathogenic bacteria. While much of the current understanding of P. syringae is centered on interactions with flowering plants, much less is known about infection in evolutionarily divergent non-flowering lineages. Here, we took a comparative evolutionary approach to understand how P. syringae infects distantly related plants. We identify broad host P. syringae isolates causing significant disease in the liverwort Marchantia polymorpha, the fern Ceratopteris richardii, and the flowering plant Nicotiana benthamiana, which last shared a common ancestor over 500 million years ago. We demonstrate that phytotoxin enriched isolates belonging to the phylogroup 2 clade of the P. syringae species complex are particularly virulent in non-flowering plants, relying on a combination of type-3 secreted effector proteins and the lipopeptide phytotoxin syringomycin. The application of purified syringomycin promotes necrosis in diverse host tissues and activates conserved genes associated with redox regulation and cell death. Toxin-deficient phylogroups normally unable to infect Marchantia thalli exhibit enhanced bacterial growth when supplemented with exogenous syringomycin, further highlighting its role as a host-range defining factor in Pseudomonas. Collectively our research reveals a key role for the lipopeptide syringomycin in promoting Pseudomonas colonization, which works in concert with type-3 effector proteins to antagonize an exceptionally wide spectrum of land plants.

plant biology↗

bioRxiv2022

The N-terminal executioner domains of NLR immune receptors are functionally conserved across major plant lineages

Nucleotide-binding domain and leucine-rich repeat (NLR) proteins are a prominent class of intracellular immune receptors that are present across diverse plant lineages. However, our understanding of plant NLR structure and function is limited to the evolutionarily young flowering plant clade (angiosperms). Here, we describe an extended spectrum of NLR diversity across major plant lineages and demonstrate functional conservation of N-terminal executioner domains that trigger immune responses. We show that broadly distributed CC (coiled-coil) and TIR (toll/interleukin-1 receptor) domains retain executioner function through trans-lineage activation of immune-related cell death in the model angiosperm Nicotiana benthamiana. Further examination of a CC subfamily specific to non-flowering lineages uncovered an essential N-terminal MAEPL motif with functional similarity to resistosome-forming CC-NLRs. Ectopic activation of the MAEPL-type CC in the divergent liverwort Marchantia polymorpha led to profound growth inhibition, defense gene activation, and signatures of cell death resembling CC activity in flowering plants. Moreover, comparative macroevolutionary transcriptomics in Marchantia and Nicotiana identified conserved CC responsive genes, providing further insight into the core aspects of CC function shared between flowering and non-flowering plants. Our findings highlight the need to understand NLR structure and function across the full spectrum of plant diversity.

plant biology↗

bioRxiv2017

Phytophthora palmivora establishes tissue-specific intracellular infection structures in the earliest divergent land plant lineage

The expansion of plants onto land was a formative event that brought forth profound changes to the Earths geochemistry and biota. Filamentous eukaryotic microbes developed the ability to colonize plant tissues early during the evolution of land plants, as demonstrated by intimate symbiosis-like associations in >400 million-year-old fossils. However, the degree to which filamentous microbes establish pathogenic interactions with early divergent land plants is unclear. Here, we demonstrate that the broad host-range oomycete pathogen Phytophthora palmivora colonizes liverworts, the earliest divergent land plant lineage. We show that P. palmivora establishes a complex tissue-specific interaction with Marchantia polymorpha, where it completes a full infection cycle within air chambers of the dorsal photosynthetic layer. Remarkably, P. palmivora invaginates M. polymorpha cells with haustoria-like structures that accumulate host cellular trafficking machinery and the membrane-syntaxin MpSYP13B but not the related MpSYP13A. Our results indicate that the intracellular accommodation of filamentous microbes is an ancient plant trait that is successfully exploited by pathogens like P. palmivora.

plant biology↗