Elucidating the role of ROS in mediating self-incompatibility induced PCD
Lead Research Organisation:
UNIVERSITY OF EXETER
Department Name: Biosciences
Abstract
Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.
Technical Summary
(A) Live-cell imaging of Arabidopsis SI lines expressing genetically encoded markers, including roGFP-Orp1 H2O2 sensors, in combination with markers/probes for various cellular organelles, will establish the intracellular sources of SI-induced ROS.
We will use the cell permeable sulfenic acid probe BCN-E-BCN, which traps sulfenic acids and, through linkage with Alexafluor dyes, allows for the fluorescence detection of sulfenylation in situ, to track the subcellular location of protein oxidation in pollen during SI.
(B) We will conduct 14C-glucose labelling assays to determine the SI-ROS induced changes in glycolytic metabolism in pollen tubes.
Using fluorometric and luminescence-based assays, we will determine if the activity of GAPDH and enolase, both subject to oxPTMs, are affected by SI-induced ROS. We will measure glycolytic/TCA cycle intermediates using LC-MS and GC-MS.
We will measure SI-induced changes in pollen energy charge using an ATP luminescence assay with luciferin. In addition, we will use a FRET-based biosensor for ATP, ATeam1.03-nD/nA, to monitor dynamics of ATP production in Arabidopsis pollen tubes and determine how this changes after SI.
We will use pharmacological inhibitors for ATP synthase, hexokinase and GAPDH, in combination with caspase-activity assays, to establish a link between reduced energy metabolism and PCD.
PM H+-ATPase (AHA7/8) T-DNA mutants in the Arabidopsis SI background will be used to evaluate their functional involvement in SI-PCD. The ratiometric pH sensor (phGFP) will be used to investigate a mechanistic link with SI-induced acidification.
We will determine SI-induced changes in the localization of GAPC in Arabidopsis "SI" plants by expressing an FP version.
(C) A series of biochemical assays with recombinant Papaver actin and ABPs, both containing oxidation resistant substitutions, will determine if oxidative modifications affect actin assembly/disassembly, and interactions with ABPs in vitro.
We will use the cell permeable sulfenic acid probe BCN-E-BCN, which traps sulfenic acids and, through linkage with Alexafluor dyes, allows for the fluorescence detection of sulfenylation in situ, to track the subcellular location of protein oxidation in pollen during SI.
(B) We will conduct 14C-glucose labelling assays to determine the SI-ROS induced changes in glycolytic metabolism in pollen tubes.
Using fluorometric and luminescence-based assays, we will determine if the activity of GAPDH and enolase, both subject to oxPTMs, are affected by SI-induced ROS. We will measure glycolytic/TCA cycle intermediates using LC-MS and GC-MS.
We will measure SI-induced changes in pollen energy charge using an ATP luminescence assay with luciferin. In addition, we will use a FRET-based biosensor for ATP, ATeam1.03-nD/nA, to monitor dynamics of ATP production in Arabidopsis pollen tubes and determine how this changes after SI.
We will use pharmacological inhibitors for ATP synthase, hexokinase and GAPDH, in combination with caspase-activity assays, to establish a link between reduced energy metabolism and PCD.
PM H+-ATPase (AHA7/8) T-DNA mutants in the Arabidopsis SI background will be used to evaluate their functional involvement in SI-PCD. The ratiometric pH sensor (phGFP) will be used to investigate a mechanistic link with SI-induced acidification.
We will determine SI-induced changes in the localization of GAPC in Arabidopsis "SI" plants by expressing an FP version.
(C) A series of biochemical assays with recombinant Papaver actin and ABPs, both containing oxidation resistant substitutions, will determine if oxidative modifications affect actin assembly/disassembly, and interactions with ABPs in vitro.
Planned Impact
Economic & Social Impact: Longer term, knowledge about self-incompatibility (SI), including understanding of how SI induced ROS are mechanistically involved in SI-PCD, may provide solutions to currently expensive F1 breeding systems. F1 hybrids are generally better and more productive than their parents, offering significant benefits to growers in terms of yield improvement, agronomic performance and consistency of end-use quality. Not surprisingly, hybrid seed comprises ~40% of global seed sales (worth billions p.a.). In the UK, for example, sugar beet, forage maize and many vegetable crops are all grown from F1 hybrid seed. Hybrid varieties also account for an increasing share of the rapeseed and winter barley market, and new hybrid wheat varieties have recently been introduced. Currently plant breeders have to hand-emasculate flowers to produce F1 hybrids. This is time-consuming and expensive. The introduction of the Papaver SI system to crops provides a potential route to produce F1 hybrids more easily and more economically. If a crop expresses the SI-PCD system it does not need to be emasculated, as all crosses will result in hybrid seed. The successful transfer of the Papaver SI system to Arabidopsis raises the possibility that a similar functional transfer is possible to other dicot crops, or even to the more distantly related grasses. This would mark a highly significant biotechnological break-through that could lead to a change in public-good and commercial breeding practises around the world. The ability to more effectively capture hybrid vigour in food crops would have profound food-security implications.
Another area through which knowledge about SI-PCD can potentially contribute to Economic and Social Impact is the development of new herbicides. Efficient herbicide systems for weed control are essential to safeguard crop yield. However, wWeeds are increasingly resistant to currently used herbicides. PCD constitutes a source of unexplored molecular targets for new herbicidal modes of action. Such new targets would avoid the use of toxic chemicals, benefiting the farmers, the agro-chemical industry, the environment and the wider public.
Fulfilling BBSRC strategic aims: This proposal sits firmly within the "Understanding the rules of life - promoting creative, curiosity-driven frontier bioscience to address fundamental questions in biology" remit of BBSRC described in the Forward Look for UK Bioscience document. While the science we propose is fundamental, there are potential applications for SI in the future (see above). Use of SI could impact on the BBSRC research priorities of "Sustainably enhancing agricultural production" and "Agriculture and food security". Providing enough food for the world is a major challenge. More economic ways to make F1 hybrid crops with better yields could provide an important contribution. Likewise, increasing our knowledge of PCD in plants can lead to the development of an innovative weed resistance management strategy. In addition, elements of the proposed research associate with "Systems approaches to the biosciences" and "Technology development for the biosciences". The proposal benefits from an "International partnership" with Shanjin Huang, Tsinghua University , Beijing, China.
The proposed research also aligns with the three themes highlighted in BBSRC's forward look for the UK bioscience: "Advancing the frontiers of bioscience discovery", "Tackling strategic challenges" (in particular "Bioscience for sustainable agriculture and food"), and "Building strong foundations".
The proposed collaborative project is novel, cutting edge, internationally competitive science and builds on well-established, high impact research, which underpins possible solutions to food security. Importantly, funding of this project is essential for the continuation of this high impact, and mostly BBSRC funded, research on plant cell signalling and PCD for the future.
Another area through which knowledge about SI-PCD can potentially contribute to Economic and Social Impact is the development of new herbicides. Efficient herbicide systems for weed control are essential to safeguard crop yield. However, wWeeds are increasingly resistant to currently used herbicides. PCD constitutes a source of unexplored molecular targets for new herbicidal modes of action. Such new targets would avoid the use of toxic chemicals, benefiting the farmers, the agro-chemical industry, the environment and the wider public.
Fulfilling BBSRC strategic aims: This proposal sits firmly within the "Understanding the rules of life - promoting creative, curiosity-driven frontier bioscience to address fundamental questions in biology" remit of BBSRC described in the Forward Look for UK Bioscience document. While the science we propose is fundamental, there are potential applications for SI in the future (see above). Use of SI could impact on the BBSRC research priorities of "Sustainably enhancing agricultural production" and "Agriculture and food security". Providing enough food for the world is a major challenge. More economic ways to make F1 hybrid crops with better yields could provide an important contribution. Likewise, increasing our knowledge of PCD in plants can lead to the development of an innovative weed resistance management strategy. In addition, elements of the proposed research associate with "Systems approaches to the biosciences" and "Technology development for the biosciences". The proposal benefits from an "International partnership" with Shanjin Huang, Tsinghua University , Beijing, China.
The proposed research also aligns with the three themes highlighted in BBSRC's forward look for the UK bioscience: "Advancing the frontiers of bioscience discovery", "Tackling strategic challenges" (in particular "Bioscience for sustainable agriculture and food"), and "Building strong foundations".
The proposed collaborative project is novel, cutting edge, internationally competitive science and builds on well-established, high impact research, which underpins possible solutions to food security. Importantly, funding of this project is essential for the continuation of this high impact, and mostly BBSRC funded, research on plant cell signalling and PCD for the future.
Organisations
People |
ORCID iD |
| Nicholas Smirnoff (Principal Investigator) |
Publications
Hsiao AS
(2022)
Bioimaging tools move plant physiology studies forward.
in Frontiers in plant science
Hsiao AS
(2022)
Plant Protein Disorder: Spatial Regulation, Broad Specificity, Switch of Signaling and Physiological Status.
in Frontiers in plant science
| Description | This project provided novel insights into the role of reactive oxygen species (ROS) and energy metabolism in self-incompatibility (SI)-induced programmed cell death (PCD). We demonstrated that SI triggers rapid metabolic disruption, including mitochondrial dysfunction, increased hydrogen peroxide (H2O2) production, cytosolic acidification, and ATP depletion. The use of the genetically encoded biosensor roGFP2-Orp1 enabled the first subcellular compartment-specific analysis of SI-induced H2O2 production, revealing oxidation in the cytosol, mitochondria, and plastids but not in the nuclei or peroxisomes. We established that SI-induced H2O2 production is linked to mitochondrial electron transport and demonstrated that inhibition of mitochondrial activity with antimycin A (AA) prevented ROS accumulation in all affected compartments. This suggests that mitochondria serve as the primary source of SI-induced ROS, with subsequent diffusion into the cytosol and plastids. We further showed that SI causes a significant decline in mitochondrial membrane potential and that this effect is strongly linked to SI-induced cytosolic Ca2+ elevation. Our findings highlight an interdependent relationship between Ca2+ signalling, ROS production, cytosolic acidification, and metabolic disruption in SI-induced PCD. An additional novel finding was the interplay between Ca2+ and cytosolic pH regulation in SI-induced PCD. While cytosolic acidification was not initially a primary objective, our data suggest that it plays a critical role in the signalling cascade. The exact mechanisms governing cytosolic pH regulation remain unclear, but this work provides new insights into its potential involvement in plant PCD and raises important questions for future research. |
| Exploitation Route | The findings from this project significantly advance our understanding of SI-induced PCD and provide a foundation for future studies on plant reproductive barriers and stress responses. Further research could: • Investigate the molecular mechanisms linking SI-induced ROS production to metabolic alterations. • Examine potential compensatory metabolic pathways that allow partial ATP maintenance despite severe mitochondrial dysfunction. • Further dissect the interplay between cytosolic pH changes and Ca2+ signalling during SI-PCD. • Use of pollen-expressed redox and ATP biosensors in pollen to investigate reasons for pollen tube sensitivity (and hence pollination and seed production) under climate change associated high temperature episodes. Insights into mitochondrial dysfunction and ROS signalling identified in this SI system could inform broader research into plant stress responses and programmed cell death mechanisms. |
| Sectors | Agriculture Food and Drink |
| Description | While this research remains in the early stages of dissemination, it has the potential to generate broader impacts beyond academia. SI is currently being developed as a technology/system to aid plant breeding in the future. The findings on SI-induced PCD provide new insights into mitochondrial function, ROS signalling, and metabolic disruption, which could eventually inform strategies for hybrid seed production by improving our understanding of SI mechanisms in plants. The discovery of cytosolic acidification as a key factor in SI-induced PCD raises new questions about the wider impact of pH regulation in plant stress responses, which has been largely unexplored to date. This could have longer-term implications for improving plant resilience under adverse environmental conditions, such as drought or pathogen attack. The impact within academia for future research is a set of verified tools (plants expressing redox and ATP biosensors in pollen) and methods to investigate pollen metabolism and redox processes in much more detail than previously possible. Reactive oxygen species (ROS) are critical for pollen tube growth as well as the SI response. Sensitivity of pollen to elevated temperatures impacts crop pollination and our collection of plants expressing the roGFP-Orp1 hydrogen peroxide biosensor in specific subcellular compartments will be used to understand the proposed role of ROS in these critical processes which are critical to food security. Though the full impact of these findings is yet to be realized, they contribute to a growing body of knowledge on plant cell fate regulation. The work may ultimately influence future research directions in plant reproduction, stress physiology, and metabolic regulation. |