Biology subjects

Hibberd, J.

Publications and source records attributed to Hibberd, J..

4 recordsLinked to original sources

bioRxiv2026

Temporal dynamics and functional divergence of the chloroplast division apparatus in Oryza sativa

O_LIChloroplast division is governed by a conserved protein machinery, yet empirical characterization of these regulators remains limited in rice, a primary target for C4 engineering. Increased chloroplast occupancy in bundle sheath cells is a hallmark of the C4 pathway and so manipulating division is a potential strategy to achieve this goal. C_LIO_LIThrough developmental transcript profiling and image analysis, we identified a discrete window of active chloroplast proliferation in rice leaves, coinciding with peak expression of conserved plastid division genes. Functional characterization via overexpression revealed regulatory behaviours distinct from those in Arabidopsis thaliana. Overexpression of OsFtsZ1&2 resulted in fewer, enlarged chloroplasts per bundle sheath cell, whereas OsMCD1&OsMinE restricted plastid expansion without altering division rates. Conversely, overexpressing OsPDV1&2 or OsARC6&OsDRP5B increased plastid size without affecting total count. When OsPDV1&2 were co-expressed with transcriptional regulator ZmG2, we observed modest increases in chloroplast size alongside reduced stomatal aperture, increased stomatal density, and higher intrinsic water-use efficiency. C_LIO_LIThe results define the temporal landscape of plastid biogenesis in rice and demonstrate divergence across lineages. Our findings suggest that manipulating the division apparatus is insufficient to drive C4-like chloroplast biogenesis in the rice bundle sheath, highlighting the complexity of plastid-host cell coordination in cereals. C_LI

Plant Biology↗

bioRxiv2025

A tRNA-gRNA multiplexing system for CRISPR genome editing in Marchantia polymorpha.

The liverwort Marchantia polymorpha is a widely used model organism for studying land plant biology, which has also proven to be a promising testbed for bioengineering. CRISPR/Cas9 technology has emerged as a transformative tool for precise genome modifications in M. polymorpha. However, a robust method for the simultaneous expression of multiple gRNAs, which is crucial for enhancing the efficiency and versatility of CRISPR/Cas9-based genome editing, has yet to be fully developed. In this study, we introduce an adaptation from the OpenPlant kit CRISPR/Cas9 tools, that facilitates expression of multiple gRNAs from a single transcript through incorporation of tRNA sequences. This approach significantly improves the efficiency and scalability of genome editing in M. polymorpha. Additionally, by combining this vector system with a simplified and optimized protocol for thallus transformation, we further streamline the generation of CRISPR/Cas9 mutants in M. polymorpha. The resulting gene- editing system offers a versatile, time-saving and straightforward tool for advancing functional genomics in M. polymorpha, enabling more comprehensive genetic modifications and genome engineering.

plant biology↗

bioRxiv2018

Quantitative variation within a species for traits underpinning C4 photosynthesis

Engineering C4 photosynthesis into C3 crops such as rice or wheat could substantially increase their yield by alleviating photorespiratory losses1,2. This objective is challenging because the C4 pathway involves complex modifications to the biochemistry, cell biology and anatomy of leaves3. Forward genetics has provided limited insight into the mechanistic basis of these characteristics and there have been no reports of significant quantitative intra-specific variation of C4 attributes that would allow trait-mapping4,5. Here we show that accessions of C4 Gynandropsis gynandra collected from locations across Africa and Asia exhibit natural variation in key characteristics of C4 photosynthesis. Variable traits include bundle sheath size and vein density, gas exchange parameters and carbon-isotope discrimination associated with the C4 state, but also abundance of transcripts encoding core enzymes of the C4 cycle. Traits relating to water use showed more quantitative variation than those associated with carbon assimilation. We propose variation in these traits likely adapted the hydraulic system for increased water use efficiency rather than improving carbon fixation, indicating that selection pressure may drive C4 diversity in G. gynandra by acting to modify water use rather than photosynthesis. As these accessions can be easily crossed and produce fertile offspring, our findings indicate that natural variation within a C4 species is sufficiently large to allow genetic-mapping of key anatomical C4 traits and regulators.

plant biology↗

bioRxiv2017

Wide sampling of natural diversity identifies novel molecular signatures of C4 photosynthesis

Introductory paragraphMuch of biology is associated with convergent traits, and it is challenging to determine the extent to which underlying molecular mechanisms are shared across phylogeny. By analyzing plants representing eighteen independent origins of C4 photosynthesis, we quantified the extent to which this convergent trait utilises identical molecular mechanisms. We demonstrate that biochemical changes that characterise C4 species are recovered by this process, and expand the paradigm by four metabolic pathways not previously associated with C4 photosynthesis. Furthermore, we show that expression of many genes that distinguish C3 and C4 species respond to low CO2, providing molecular evidence that reduction in atmospheric CO2 was a driver for C4 evolution. Thus the origin and architecture of complex traits can be derived from transcriptome comparisons across natural diversity.

plant biology↗