Professor Hilary Rogers

Plant Organ senescence

A) SAG21/AtLEA5 a gene at the interface between stress responses and senescence

SAG21 belongs to the late embryogenesis-associated (LEA) protein family. Although it has been implicated in growth and redox responses, its precise roles remain obscure. To address this problem, in collaboration with  Prof Christine Foyer (Leeds) and Prof Frederica Theodolou (Rothamsted Research) we characterised root and shoot development and response to biotic stress in SAG21 over-expressor (OEX) and antisense (AS) lines. AS lines exhibited earlier flowering and senescence and reduced shoot biomass  (Mohd Salleh et al, 2012)

Expression of SAG21 is induced by numerous abiotic stresses  and in collaboration with Prof. Luis Mur (IBERS Aberystwyth) we also investigated whether perturbation of SAG21 affected growth of pathogens. We found that growth of the fungal nectroph, Botrytis cinerea and of a virulent bacterial pathogen (Pseudomonas syringae pv. tomato) was affected by SAG21 expression, however growth of an avirulent P.syringae strain was unaffected . In collaboration with Prof. John Runions (Oxford Brookes) we showed that a SAG21 -YFP fusion was localised to mitochondria, raising the intriguing possibility that SAG21 interacts with proteins involved in mitochondrial ROS signalling which in turn, impacts on root development and pathogen responses.

B) Floral Development and Senescence

Floral senescence in many species is largely controlled by the plant growth regulator ethylene. However, the senescence of many economically important species is not ethylene sensitive and therefore the techniques presently available are ineffectual at prolonging their storage or vase life. How floral senescence and tepal abscission in these species is regulated remains an interesting biological question. In collaboration with Dr A Stead (Royal Holloway),  Dr Loremnzo Mariotti (Pisa) and Prof Sergi-Munné-Bosch (Barcelona), and using transcriptomic analysis we have identified patterns of auxin response factor genes (ARF) in lilies  suggesting conservation of auxin-regulated abscission pathways in ethylene-insensitive flowers (Lombardi et al., 2014). The role of reactive oxygen species (ROS) in petal senescence is far from clear (Rogers, 2012; Rogers, and Munne-Bosch, 2016) and we are currently studying genes related to ROS and stress during petal senescence (Salleh et al., 2016).

We were also interested in discovering effects of environmental stress such as ambient dehydration and cold storage on flower opening and senescence through changes in global gene expression. This has implications both for understanding the regulation of senescence regulatory networks and has practical implications in the cut flower industry where flowers are often stored in suboptimal conditions during the transport chain. Microarray analysis revealed that there was significant sharing of gene expression between developmental senescence and an ambient dry stress treatment, whereas cold induced a distinct profile of transcripts (Wagstaff et al., 2010) . Currently we are investigating how lily flower opening is affected by cold storage, how senescence is coordinated in complex flowers such as dahlia, and transcriptional changes in rose pedicels  post-harvest.

C) Post-harvest senescence

Fresh fruit and vegetables are a key component of  a healthy diet, but fresh produce is also very perishable. We are developing new tools and understanding of underlying molecular processes to improve safety and quality fruits and salads (https://cordis.europa.eu/project/id/289719/reporting). Ready to eat salads are taking an increasing market share of fresh fruit and vegetable sales especially in Northern Europe. However they have a very short shelf life and, if handled inappropriately, can become contaminated with pathogenic organisms posing a serious health risk to consumers.  Together with Dr Carsten Muller and Dr Cedric Berger we are using state of the art thermal desorption gas chromatography mass spectrometry (TD-GC-MS ToF) to detect volatile organic compounds that can be applied as markers for quality and safety of fresh cut produce (Spadafora et al., 2016; ; Amaro et al., 2018; Spadafora et al., 2019; Muto et al., 2020). Our TD-GC-MS ToF work is in collaboration with Markes International. We are also using transcriptomic analysis to better understand regulatory mechanisms related to postharvest changes in fruit and salads (Cavaioulo et al., 2017). In a recent Innovate UK project collaborating with Cranfield University and JGHC ( asparagus growers) we are using transcriptomic approaches and cellular analysis to investigate post-harvest tip rots that severely limits asparagus shelf life.

Stress memory in plants is a growing area of reserach, helping to explain how plants cope with abiotic stresses, and how exposure to stres during growth affects post-harvest resilience. In a BBSRC-funded project, in collaboration with   Prof Alison Kingston-Smith (IBERS Aberystwyth) we are investigating how pre-harvest stress designed to simulate predicted future cllimate scnearios affects responses of grass leaves to the environment inside the rumen.

Effects of stress on cell division

Plants are subject to numerous stresses including DNA damaging agents such as uv, soil pollutants and saline environments. Many of these agents cause an arrest in cell division until favourable conditions allow growth to resume. In collaboration with Dr Dennis Francis (Cardiff) , Prof M Beatrice Bitonti (University of Calabria) and  Dr. Robert Herbert (University of Worcester) we have been studying genes that regulate these responses. DNA damage induces a cell cycle checkpoint arresting cells at G2/M One of the key regulators of this process in plants is WEE1 kinase which inactivates the the cyclin dependent kinase (CDK) by phosphorylation. We have have shown using a yeast-two hybrid screen that Arabidopsis WEE1 interacts with proteins involved with proteasome-mediated degradation (Cook et al., 2013), and that expression of the Arabidopsis WEE1 gene in tobacco cells results in an unexpected dominant negative effect (Siciliano et al., 2019).

We are also interested in how abiotic stresses such as salinity affect cell division and callus growth. Salinity is a major abiotic stress that limits plant productivity. Plants respond to salinity by switching on a coordinated set of physiological and molecular responses that can result in acclimation. We focussed on Medicago truncatula an important model legume species to test whether acclimation could enhance NaCl and osmotic tolerance in calli. In long term culture calli became tolerant to 150 mM  NaCl, and to osmotic stress and showed enhanced expression of genes linked to cell division (such as WEE1)  (El Maghrabi et al., 2013; 2017). Moreover, salt stress resulted in nuclear marginalisation in the cell, acting as a consistent marker of salt tolerance (El Maghrabi et al., 2019).

Mycelial interactions between competing fungi and fungal ecology

In forest ecosystems, wood decay fungal communities are key decomposers. Interactions between different decomposer species can result in deadlock or overgrowth by one of the competitors, and these interactions affect how comunities develop and rates of decomposition.  In collaboration with Prof Lynne Boddy, and Prof Dan Eastwood, (Swansea) we have been using high throughput sequencing approaches to understand the succession of fungal colonisation of fallen wood (Eyre et al 2010)  We have also been studying how future climate scenarios will affect these interactions (Hiscox et al., 2015; 2016)  Our analysis indicates that  changes in gene expression are related to the outcome of interactions  and that temperature changes will affect outcomes of fungal competition (O'Leary et al., 2019)

Other collaborative projects

A) Fungal taxonomy and population biology

In collaboration with Prof Lynne Boddy and Dr Martyn Ainsworth (Kew Gardens) we have been using targeted PCR primers in support of conservation efforts of rare UK fungi. We were able to show that Hericium species that fruit rarely are present as endophytes in the sapwood of many tree species (Parfitt et al, 2007). We have also used ITS sequencing to help to clarify taxonomic relationships within Hydnellum and Phellodon, which are often difficult to distinguish based on morphology (Ainsworth et al., 2009) , revealing the presence of cryptic species. Current work is aimed at understanding how fungal community structures develop in heart-rot of  veteran and ancient beech and oak trees. These are important as they provide habitats for a wide range of saproxylic invertebrates, vertebrates, and fungi, including rare/endangerd species.

B) The role of polyamines in plant development

Polyamines are essential metabolites in plants with important roles in stress responses, development and senescence. In collaboration with Prof Alessandra Cona (Roma Tre) we are investigating how mutation of copper-containing amine oxidases affect plant grwoth and senescence.

Staff currently associated with research:

• Sarah Christofides (PDRA stress memory in grasses)
• Swapna Nayakoti (asparagus project)
• Richard Ludlow (recent postgraduate on post-harvest biology of garlic)
• Lama Alotaibi (PhD student - stress memory in salads)
• Ashley Baldwin (DTP PhD student - strawberry shelf life)
• Rakhee Dhorajiwala (DTP PhD student - lily flower opening)
• Nico Bruyniks (DTP PhD student - salad contamination)

Other international collaborations

• Prof Diego Albani (University of Sassari, Sardinia, Italy) on the cell cycle
• Prof M. Beatrice Bitonti and Dr Leonardo Bruno (University of Calabria, Italy) on postharvest changes in peached
• Prof Antonio Ferrante (University of Milano, Italy) on postharvest stress responses
• Dr Wan Liu (China) on stress responses