Periodic Reporting for period 1 - UNROPO (Unlocking de novo Rooting Potential)
Période du rapport: 2023-05-01 au 2025-10-31
Plants demonstrate an unparalleled capacity for regeneration, a unique feature that is widely exploited in modern agriculture and forestry for the asexual propagation of elite, pest- and disease-resistant species, genotypes and clones. However, even among plants, significant variation in regenerative potential can be observed. In particular, the regeneration efficiency of tree species varies greatly. This poses an economic problem, given that commercial forestry relies on the vegetative reproduction of elite genotypes selected from available genetic diversity. An important step in tree propagation is inducing new roots following the excision of stem tissue — a process known as propagation through cuttings. The inflicted damage typically triggers cells at the wound site to acquire stem cell-like characteristics, which in turn allow the de novo formation of root primordia.
The acquisition of stem cell identity by cells located next to wounded tissue relies on the activity of specific ERF-type transcription factors. These transcription factors are part of a synergistic wound response involving the accumulation of the phytohormone auxin and ERF expression, which grants stem cell identity. Although jasmonate (JA), a stress hormone, has been proposed as a trigger of ERF expression, ERF expression can still be observed following wounding in a JA receptor knockout background. This suggests the presence of additional, as yet unknown, signalling molecules that instigate expression.
Pectin is a major component of plant cell walls and is synthesized, modified and broken down by over 300 different genes. Our proof-of-concept data suggest that pectin modifications and breakdown products may act as primary signals for expression of the regeneration driving ERF transcription factor genes. Through identification of the pre-wound pectin variants and the pectin fragments released following wounding, and elucidating the mechanisms by which these pectin breakdown products are biosynthesized and sensed, we aim to develop propagation strategies for a wider range of plant species, with a particular focus on expanding the spectrum of tree species that can be propagated by stem cuttings.
The acquisition of stem cell identity by cells located next to wounded tissue relies on the activity of specific ERF-type transcription factors. These transcription factors are part of a synergistic wound response involving the accumulation of the phytohormone auxin and ERF expression, which grants stem cell identity. Although jasmonate (JA), a stress hormone, has been proposed as a trigger of ERF expression, ERF expression can still be observed following wounding in a JA receptor knockout background. This suggests the presence of additional, as yet unknown, signalling molecules that instigate expression.
Pectin is a major component of plant cell walls and is synthesized, modified and broken down by over 300 different genes. Our proof-of-concept data suggest that pectin modifications and breakdown products may act as primary signals for expression of the regeneration driving ERF transcription factor genes. Through identification of the pre-wound pectin variants and the pectin fragments released following wounding, and elucidating the mechanisms by which these pectin breakdown products are biosynthesized and sensed, we aim to develop propagation strategies for a wider range of plant species, with a particular focus on expanding the spectrum of tree species that can be propagated by stem cuttings.
A collection of Arabidopsis loss-of-function mutants was generated using genome editing techniques. This collection is in the process of being systematically tested in a diverse set of regeneration-triggering assays. Already now, several mutants with highly increased regeneration rates were identified. These lines will undergo biochemical analysis to identify pectin variants linked to regeneration potential. In parallel, a genetic screening method was developed to screen for signalling components operating downstream of pectin variants that activate regeneration.
Independently, we aim to link the rooting potential of poplar cuttings with cell wall composition. Poplar is one of the most important economically valuable tree species in temperate regions of the world. Intensive plantations use propagation by cutting for most poplar genotypes. However, significant differences in the degree of rooting can be observed among the natural variation of poplar. This makes poplar a particularly suitable model system in which to study the genetic control of rooting. In collaboration with INRAe (France) and CREA (Italy) a collection of over 300 poplar eastern cottonwood trees is being used to correlate rooting efficiency with whole genome sequencing and cell wall metabolome data
Independently, we aim to link the rooting potential of poplar cuttings with cell wall composition. Poplar is one of the most important economically valuable tree species in temperate regions of the world. Intensive plantations use propagation by cutting for most poplar genotypes. However, significant differences in the degree of rooting can be observed among the natural variation of poplar. This makes poplar a particularly suitable model system in which to study the genetic control of rooting. In collaboration with INRAe (France) and CREA (Italy) a collection of over 300 poplar eastern cottonwood trees is being used to correlate rooting efficiency with whole genome sequencing and cell wall metabolome data
A collection of 2,500 knockout plants in different sets of pectin genes was established, which represents a valuable resource for the plant community. Alongside our working hypothesis that pectin steers regeneration, pectin also plays a role in many other biological processes, including pathogen recognition, root hair and pollen tube growth, and phyllotaxis. Through collaboration, we aim to study other pectin-related processes.