Howard Thomas (scientist)

Last updated
Howard Sidney Thomas

FWIP FLSW
Born1948
Died2022
NationalityBritish
Known forplant senescence; jazz; science communication
SpouseHelen Ougham
Scientific career
InstitutionsWelsh Plant Breeding Station; University of Aberystwyth, Wales
Website sidthomas.net

Howard Sidney (Sid) Thomas, FWIF, FLSW (1948 - 2022) was a plant scientist at the Welsh Plant Breeding Station and later the University of Aberystwyth, and also a jazz musician and composer. He became Emeritus Professor of Biological, Environmental and Rural Sciences, University of Aberystwyth. [1]

Contents

Career

Thomas studied at University of Aberystwyth and was later awarded the DSc degree by the same University. [2] He started his career in the 1960s at the Welsh Plant Breeding Station in Aberystwyth, Wales. He worked on breeding improved varieties of forage grasses and grains, including oats and barley. He made use of cytogenetic methods. [3] He also investigated how grass leaves yellowed and died, since prolonging active green leaves would improve their value as forage. He collaborated with other researchers to bring new technologies into the studies. His work moved into research on photosynthesis, effects of temperature on grasses and also developing an understanding of the differences in biochemistry and lipid metabolism as leaves died. This work made a substantial contribution to the understanding of the catabolism of chloroplasts and chlorophylls. [4] [5] He began to apply computing to his data from the 1980s as small microcomputers became available.

His work led to the identification of non-yellowing mutants of grasses, subsequently termed a 'stay-green' phenotype, [6] and then more detailed genetic study to characterise their differences from typical grasses. [7] Initially using classical genetics methods but later molecular genetics, Thomas and his collaborators identified a gene, Sid ((senescence-induced degradation), the protein product of which stabilised the pigment-protein-lipid complexes of chloroplasts so that dying leaves remained green. [8] A mutation in the phaeophorbide a dioxygenase gene was later identified as the reason for the phenotype. Later, collaborating with researchers in Switzerland and the USA using molecular genetics, functional analysis and cell biology in pea, Arabidopsis, rice and Festuca pratensis, the researchers showed that this gene was one that Gregor Mendel recorded in 1866 that resulted in green or yellow cotyledons. [9]

Thomas held visiting professorships at the Universities of California, Bern and Zurich. Later in his career he was the head of cell and molecular biology research and a member of the management board at the Institute of Grassland and Environmental Research. [2]

He was also involved in public communication around plants, including investigating the concept of plant blindness. [10] as well as promoting links between science and the arts. He participated in the Hay Literary Festival in 2013 in a panel discussion about Shakespeare and sustainability with English scholars. [11] Thomas collaborated with Jayne Archer and Richard Marggraf Turley. This work also threw light on the significance of crop weeds such as darnel in King Lear. [12] [13]

Publications

Thomas was the author or co-author of over 200 scientific publications and books. Among the most significant were:

Honours and awards

Thomas was a Fellow of the Learned Society of Wales (elected 2014) [14] and of the Linnean Society. [15]

Personal life

Thomas was married to Helen Ougham. [16] He died 12 July 2022. [17]

Related Research Articles

<span class="mw-page-title-main">Chloroplast</span> Plant organelle that conducts photosynthesis

A chloroplast is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in the energy-storage molecules ATP and NADPH while freeing oxygen from water in the cells. The ATP and NADPH is then used to make organic molecules from carbon dioxide in a process known as the Calvin cycle. Chloroplasts carry out a number of other functions, including fatty acid synthesis, amino acid synthesis, and the immune response in plants. The number of chloroplasts per cell varies from one, in unicellular algae, up to 100 in plants like Arabidopsis and wheat.

<span class="mw-page-title-main">Chlorophyll</span> Green pigments found in plants, algae and bacteria

Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words χλωρός, khloros and φύλλον, phyllon ("leaf"). Chlorophyll allow plants to absorb energy from light.

<span class="mw-page-title-main">Photosynthesis</span> Biological process to convert light into chemical energy

Photosynthesis is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their activities. Photosynthetic organisms use intracellular organic compounds to store the chemical energy they produce in photosynthesis. Photosynthesis is usually used to refer to oxygenic photosynthesis, a form of photosynthesis where the photosynthetic processes produce oxygen as a byproduct and synthesize carbohydrate molecules like sugars, starches, glycogen, and cellulose to store the chemical energy. To use the chemical energy stored in these organic compounds, the organisms' cells metabolize the organic compounds through another process called cellular respiration. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and it supplies most of the biological energy necessary for complex life on Earth.

<span class="mw-page-title-main">Plastid</span> Plant cell organelles that perform photosynthesis and store starch

A plastid, pl. plastids, is a membrane-bound organelle found in the cells of plants, algae, and some other eukaryotic organisms. They are considered to be intracellular endosymbiotic cyanobacteria.

<span class="mw-page-title-main">Thylakoid</span> Membrane enclosed compartments in chloroplasts and cyanobacteria

Thylakoids are membrane-bound compartments inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen. Chloroplast thylakoids frequently form stacks of disks referred to as grana. Grana are connected by intergranal or stromal thylakoids, which join granum stacks together as a single functional compartment.

<span class="mw-page-title-main">Pyrenoid</span> Organelle found within the chloroplasts of algae and hornworts

Pyrenoids are sub-cellular micro-compartments found in chloroplasts of many algae, and in a single group of land plants, the hornworts. Pyrenoids are associated with the operation of a carbon-concentrating mechanism (CCM). Their main function is to act as centres of carbon dioxide (CO2) fixation, by generating and maintaining a CO2 rich environment around the photosynthetic enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). Pyrenoids therefore seem to have a role analogous to that of carboxysomes in cyanobacteria.

<span class="mw-page-title-main">Chromoplast</span> Pigment-bearing organelle in plant cells

Chromoplasts are plastids, heterogeneous organelles responsible for pigment synthesis and storage in specific photosynthetic eukaryotes. It is thought that like all other plastids including chloroplasts and leucoplasts they are descended from symbiotic prokaryotes.

<span class="mw-page-title-main">Photosystem</span> Structural units of protein involved in photosynthesis

Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons. Photosystems are found in the thylakoid membranes of plants, algae, and cyanobacteria. These membranes are located inside the chloroplasts of plants and algae, and in the cytoplasmic membrane of photosynthetic bacteria. There are two kinds of photosystems: PSI and PSII.

<span class="mw-page-title-main">Photosystem I</span> Second protein complex in photosynthetic light reactions

Photosystem I is one of two photosystems in the photosynthetic light reactions of algae, plants, and cyanobacteria. Photosystem I is an integral membrane protein complex that uses light energy to catalyze the transfer of electrons across the thylakoid membrane from plastocyanin to ferredoxin. Ultimately, the electrons that are transferred by Photosystem I are used to produce the moderate-energy hydrogen carrier NADPH. The photon energy absorbed by Photosystem I also produces a proton-motive force that is used to generate ATP. PSI is composed of more than 110 cofactors, significantly more than Photosystem II.

Chlorophyll <i>a</i> Chemical compound

Chlorophyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light, and it is a poor absorber of green and near-green portions of the spectrum. Chlorophyll does not reflect light but chlorophyll-containing tissues appear green because green light is diffusively reflected by structures like cell walls. This photosynthetic pigment is essential for photosynthesis in eukaryotes, cyanobacteria and prochlorophytes because of its role as primary electron donor in the electron transport chain. Chlorophyll a also transfers resonance energy in the antenna complex, ending in the reaction center where specific chlorophylls P680 and P700 are located.

<span class="mw-page-title-main">Etioplast</span>

Etioplasts are an intermediate type of plastid that develop from proplastids that have not been exposed to light, and convert into chloroplasts upon exposure to light. They are usually found in stem and leaf tissue of flowering plants (Angiosperms) grown either in complete darkness, or in extremely low-light conditions.

<span class="mw-page-title-main">Autumn leaf color</span> Phenomenon that affects the leaves during autumn

Autumn leaf color is a phenomenon that affects the normally green leaves of many deciduous trees and shrubs by which they take on, during a few weeks in the autumn season, various shades of yellow, orange, red, purple, and brown. The phenomenon is commonly called autumn colours or autumn foliage in British English and fall colors, fall foliage, or simply foliage in American English.

<span class="mw-page-title-main">Photoinhibition</span>

Photoinhibition is light-induced reduction in the photosynthetic capacity of a plant, alga, or cyanobacterium. Photosystem II (PSII) is more sensitive to light than the rest of the photosynthetic machinery, and most researchers define the term as light-induced damage to PSII. In living organisms, photoinhibited PSII centres are continuously repaired via degradation and synthesis of the D1 protein of the photosynthetic reaction center of PSII. Photoinhibition is also used in a wider sense, as dynamic photoinhibition, to describe all reactions that decrease the efficiency of photosynthesis when plants are exposed to light.

<span class="mw-page-title-main">Chlorophyllase</span> Enzyme in chlorophyll metabolism

Chlorophyllase is an essential enzyme in chlorophyll metabolism. It is a membrane proteins commonly known as chlase (EC 3.1.1.14, CLH) with systematic name chlorophyll chlorophyllidohydrolase. It catalyzes the reaction

<span class="mw-page-title-main">Protochlorophyllide</span> Chemical compound

Protochlorophyllide, or monovinyl protochlorophyllide, is an intermediate in the biosynthesis of chlorophyll a. It lacks the phytol side-chain of chlorophyll and the reduced pyrrole in ring D. Protochlorophyllide is highly fluorescent; mutants that accumulate it glow red if irradiated with blue light. In angiosperms, the later steps which convert protochlorophyllide to chlorophyll are light-dependent, and such plants are pale (chlorotic) if grown in the darkness. Gymnosperms, algae, and photosynthetic bacteria have another, light-independent enzyme and grow green in the darkness as well.

A gerontoplast is a plastid that develops from a chloroplast during the senescing of plant foliage. Gerontoplast development is generally seen to be the process of grana being unstacked, loss of thylakoid membranes, and large accumulation of plastoglobuli.

Antheraxanthin is a bright yellow accessory pigment found in many organisms that perform photosynthesis. It is a xanthophyll cycle pigment, an oil-soluble alcohol within the xanthophyll subgroup of carotenoids. Antheraxanthin is both a component in and product of the cellular photoprotection mechanisms in photosynthetic green algae, red algae, euglenoids, and plants.

In molecular biology, the red chlorophyll catabolite reductase family of proteins consists of several red chlorophyll catabolite reductase proteins. Red chlorophyll catabolite (RCC) reductase (RCCR) and pheophorbide (Pheide) a oxygenase (PaO) catalyse the key reaction of chlorophyll catabolism, porphyrin macrocycle cleavage of Pheide a to a primary fluorescent catabolite (pFCC).

Pheophorbide a oxygenase (EC 1.14.15.17, pheide a monooxygenase, pheide a oxygenase, PAO) is an enzyme with systematic name pheophorbide-a,NADPH:oxygen oxidoreductase (biladiene-forming). This enzyme catalyses the following chemical reaction

<span class="mw-page-title-main">Photoautotrophism</span> Organisms that use light and inorganic carbon to produce organic materials

Photoautotrophs are organisms that can utilize light energy from sunlight and elements from inorganic compounds to produce organic materials needed to sustain their own metabolism. This biological activity is known as photosynthesis, and examples of such photosynthetic organisms include plants, algae and cyanobacteria.

References

  1. ↑ "Howard (Sid) Thomas". New Phytologist Foundation. Retrieved 14 March 2023.
  2. 1 2 "The Molecular Life of Plants". Plant Molecular Biology. Wiley.
  3. ↑ Thomas, Howard; Jones, Mair Lloyd (1964). "Cytological studies of pentaploid hybrids and a synthetic decaploid in Avena". Chromosoma. 15 (2): 132–139. doi:10.1007/BF00285725. S2CID   21531079.
  4. ↑ Thomas, Howard; Stoddart, John L (1975). "Separation of Chlorophyll Degradation from Other Senescence Processes in Leaves of a Mutant Genotype of Meadow Fescue (Festuca pratensis L.)". Plant Physiology. 56 (3): 438–441. doi:10.1104/pp.56.3.438. PMC   541840 . PMID   16659320.
  5. ↑ Thomas, Howard; Luthy, Barbara; Matile, Philippe (1985). "Leaf senescence in a non-yellowing mutant of Festuca Huds. Oxidative chlorophyll bleaching by thylakoid membranes during senescence". Planta. 164 (3): 400–405. doi:10.1007/BF00402953. PMID   24249611. S2CID   11394723.
  6. ↑ Bachmann, Andre; Fernandez-Lopez, Jose; Ginsburg, Samuel; Thomas, Howard; Bouwcamp, John C; Solomos, Theophanes; Matile, Phillipe (1994). "Stay-green genotypes of Phaseolus vulgaris L.: chloroplast proteins and chlorophyll catabolites during foliar senescence". New Phytologist. 126 (4): 593–600. doi: 10.1111/j.1469-8137.1994.tb02953.x .
  7. ↑ Harwood, J L; Jones, A V H M; Thomas, H (1982). "Leaf senescence in a non-yellowing mutant of Festuca pratensis. 3: Total acyl lipids of leaf tissue during senescence". Planta. 156 (2): 152–157. doi:10.1007/BF00395429. JSTOR   23375829. PMID   24272310. S2CID   24862976.
  8. ↑ Thomas, Howard (1987). "Sid: a Mendelian locus controlling thylakoid membrane disassembly in senescing leaves of Festuca pratensis". Theoretical and Applied Genetics. 73 (4): 551–555. doi:10.1007/BF00289193. PMID   24241112. S2CID   25490555.
  9. ↑ Arnstead, Ian; Donnison, Iain; Aubry, Sylvain; others, and 11 (2007). "Cross-Species Identification of Mendel's I Locus". Science. 315: 73. doi:10.1126/science.1132912.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  10. ↑ Thomas, Howard; Ougham, Helen; Sanders, Dawn (2022). "Plant blindness and sustainability". International Journal of Sustainability in Higher Education. 23: 41–57. doi:10.1108/IJSHE-09-2020-0335. S2CID   234219965.
  11. ↑ "Shakespeare and Sustainability". University of Aberystwyth. Retrieved 16 March 2023.
  12. ↑ Balch, Oliver (2014-05-01). "Can Shakespeare and Keats address today's food security challenges?". The Guardian. Retrieved 2018-01-15.
  13. ↑ Archer, Jayne Elisabeth; Thomas, Howard; Marggraf Turley, Richard (2015). "Reading Shakespeare with the grain: sustainability and the hunger business". Green Letter. 19: 8–20. doi:10.1080/14688417.2014.985242. hdl: 2160/36427 . Retrieved 16 March 2023.
  14. ↑ "Professor Howard Thomas FWIF FLSW". The Learned Society of Wales - Cymdeithas Ddysgedig Cymru.
  15. ↑ "Professor Howard Thomas, 1948 – 2022". The Learned Society of Wales - Cymdeithas DDysgedig Cymru. Retrieved 16 March 2023.
  16. ↑ Thomas, Howard. "Howard Sidney Thomas". Howard Sidney Thomas. Retrieved 16 March 2023.
  17. ↑ Lindsey, Keith. "Howard (Sid) Thomas". New Phytologist Foundation. Retrieved 14 March 2023.
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