Analysis of the molecular and physiological effects following treatment with BC204 in Arabidopsis thaliana and Solanum lycopersicum
| dc.contributor.advisor | Hills, Paul N. | en_ZA |
| dc.contributor.author | Loubser, Johannes | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics. Institute for Plant Biotechnology | en_ZA |
| dc.date.accessioned | 2020-10-26T13:25:13Z | |
| dc.date.accessioned | 2021-02-01T07:54:26Z | |
| dc.date.available | 2020-10-26T13:25:13Z | |
| dc.date.available | 2021-02-01T07:54:26Z | |
| dc.date.issued | 2020-12 | |
| dc.description | Thesis (PhDAgric)--Stellenbosch University, 2020. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Plant biostimulants have been earmarked as one of the pivotal role players in the next much-needed agricultural revolution. Plant biostimulants are mostly from natural sources and they do not directly provide the plant with any nutrients. To date, many different biostimulants have been produced and tested on several different plant species. Although several reports indicate that they elicit an increase in overall plant growth, induce resistance to both abiotic and biotic stresses, increase crop yield and improve fruit/vegetable quality, the molecular data to back up these claims has generally been missing. One such plant biostimulant, BC204, is a citrus-based plant extract used on a variety of crop species in South Africa, China and Australia. There are internal reports from tests conducted by the producers of BC204 which show that it elicits physiological responses such as an increase in crop yield and fruit quality. One postgraduate research study reported that Croplife, a product closely related to BC204, has the potential to improve water utilisation efficiency in table grape cultivars (Van Zyl, 2007). However, no molecular data is available to explain the specific mechanisms associated with the increase in plant growth and tolerance to environmental stresses. Environmental stress is predicted to worsen due to climate change, but also due to irrigation practices on arable land areas, which can result in soil salinity. Although some progress has been made towards understanding plant mechanisms towards salt tolerance in efforts to combat the negative effects of salinity, these mechanisms are still a long way from being fully understood. BC204, like other plant biostimulants, could be a short-term alternative whilst salt tolerance and other abiotic stress mechanisms in plants are further unravelled. Such biostimulants can also be used to study salt tolerance, as the first part of this study provides preliminary evidence that BC204 significantly alleviates salt stress in Arabidopsis thaliana. BC204 treatment increased chlorophyll content, fresh and dry weights, whilst reducing proline, anthocyanin and malondialdehyde content in the presence of 10ds·m-1 EC salt stress. Stomatal conductivity was also reduced by BC204 in source leaves. In addition, BC204 had a significant effect on the expression of salinity-related genes, stimulating the expression of salinity-related genes RD29A and SOS1 independently of NaCl-stress, whilst suppressing the expression of SOT1 and P5CS1. In the second part of study, an RNA-seq approach was adopted to elucidate the effects of BC204 at the molecular level in the model plant species, Arabidopsis thaliana. BC204, applied via a soil drench at a low concentration of 0.01% (v/v), stimulated above-ground biomass production whilst eliciting a large change in gene expression levels across several biochemical pathways in Arabidopsis thaliana. Of the entire transcriptomic profile examined, a total of 8.212% of genes were significantly differentially expressed between the treated and control groups, of which 5.136% were upregulated and 3.076% downregulated. Most notably, genes involved photosynthesis, several aspects of cell wall metabolism, carbohydrate metabolism, signalling, stress and secondary metabolism were upregulated, which could explain the increase in plant growth. Genes related to transcription and RNA regulation were both strongly up- and downregulated, which suggests that BC204 plays a role in inducing and suppressing several pathways. In the third part of this study, the same RNA-seq approach was adopted to elucidate the effect of BC204 in Solanum lycopersicum, an important model crop species, at the molecular level under unstressed conditions. BC204, applied via foliar spray at a concentration of 0.05% (v/v), stimulated tomato root and shoot biomass production, root and shoot length and stem width compared to the untreated control plants. Of the 33308 transcripts analysed, a total of 18.059% genes were significantly differentially expressed between the control and treated groups, of which 8.776% were upregulated and 9.283% downregulated. Most notably, genes involved in signalling, stress and protein metabolism were upregulated, which could explain the increased growth that was observed. In both plant species, BC204 seemed to induce pathways involved in several environmental stresses. Together, the results of this study provide evidence that BC204 elicits a major change in a variety of metabolic processes which forms part of a complex network activating a broad priming response. These priming responses seem to start with enhanced photosynthesis, allowing additional energy to be channelled towards complex metabolic changes through RNA regulation and signalling. Very few metabolic plant processes seem to be unaffected by BC204 treatment. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Plantbiostimulante is geoormerk as een van die belangrikste rolspelers in die volgende broodnodige landbou-rewolusie. Plantbiostimulante word meestal onttrek uit natuurlike bronne en voorsien nie direk die plant van voedingstowwe nie. Tot op hede is baie soorte plantbiostimulante geproduseer en getoets op verskillende plantsoorte en alhoewel verskeie verslae aandui dat dit 'n toename in algehele plantgroei tot gevolg het, weerstand teen abiotiese sowel as biotiese spanning veroorsaak het, die oesopbrengs verhoog is en die vrugte / groente-kwaliteit verbeter het, ontbreek die molekulêre gegewens om hierdie aansprake te ondersteun. BC204 is 'n sitrus-gebaseerde plantuittreksel wat as 'n plantbiostimulant gebruik word vir 'n verskeidenheid plantsoorte in Suid-Afrika, China en Australië. Alhoewel daar verslae is dat dit fisiologiese reaksies ontlok, soos 'n toename in gewasopbrengs en vrugkwaliteit, is daar geen molekulêre gegewens beskikbaar om die spesifieke meganismes te verduidelik wat verband hou met die toename in plantgroei en verdraagsaamheid teenoor omgewings-stressors nie. Een nagraadse navorsingsstudie het verslag gelewer dat Croplife, ‘n produk nabyverwant aan BC204, die potensiaal het om waterverbruik effektiwiteit in tafeldruiwe kultivars te verbeter (Van Zyl, 2007). Hierdie tipe stressors sal na verwagting vererger as gevolg van klimaatsverandering, maar ook as gevolg van besproeiingspraktyke in bewerkbare gebiede. Alhoewel daar 'n mate van vordering gemaak is met betrekking tot die begrip van plantmeganismes ten opsigte van souttoleransie in die pogings om die negatiewe gevolge van soutgehalte te bekamp, is hierdie meganismes grootliks onbekend. BC204, soos ander plantbiostimulante, kan 'n korttermyn alternatief wees terwyl souttoleransie en ander abiotiese stresmeganismes in plante verder ontrafel word. Sulke biostimulante kan ook gebruik word om soutverdraagsaamheid te bestudeer, aangesien die eerste deel van hierdie studie voorlopige bewys lewer dat BC204 soutstres in Arabidopsis thaliana aansienlik verlig. Met die behandeling van BC204 het die chlorofil-inhoud, vars en droë gewigte verhoog, terwyl die inhoud van prolien, antosianien en malondialdehied in die teenwoordigheid van 10ds · m-1 EC soutstres verlaag is. Blaarhuidmondjie geleiding is ook verminder deur BC204 en NaCl in die bronblare. Verder het BC204 'n beduidende invloed op die uitdrukking van soutreaktiewe-gene gehad, wat die uitdrukking van soutgereaktiewe-gene RD29A en SOS1 onafhanklik van NaCl-spanning stimuleer, terwyl die uitdrukking van SOT1 en P5CS1 onderdruk is. In die tweede deel van die studie is 'n RNS-seq-benadering aangewend om die gevolge van BC204 op molekulêre vlak by die modelle plantspesies, Arabidopsis thaliana, toe te lig. BC204, toegedien via 'n gronddeurdrenking met 'n lae konsentrasie van 0.01% (v / v), stimuleer bogrondse biomassa-produksie, terwyl dit 'n groot verandering in geen-uitdrukkingsvlakke oor verskeie biochemiese padweë in Arabidopsis thaliana ontlok. Van die hele transkriptomiese profiel wat ondersoek is, is 'n totaal van 8.212% van die gene beduidend onderskeibaar tussen die behandelde groepe en die kontrolegroepe, waarvan 5.366% geherreguleer en 3.076% afgereguleer is. Die belangrikste veranderinge is die toename in uitdrukking van gene wat fotosintese, verskeie aspekte rondom selwand metabolisme, koolhidraatmetabolisme, seine, spanning en sekondêre metabolisme insluit, wat die toename in plantgroei kan verklaar. Die uitdrukking van gene wat met transkripsie en RNS-regulering verband hou, het beide sterk toegeneem ena afgeneem, wat daarop dui dat BC204 'n rol speel in die induksie en onderdrukking van verskeie padweë. In die derde deel van hierdie studie is dieselfde RNS-seq-benadering gebruik om die effek van BC204 in Solanum lycopersicum, 'n belangrike plantmodelspesie, op molekulêre vlak onder onbedrukte toestande toe te lig. BC204, toegedien via blaarbespuiting met 'n lae konsentrasie van 0.05%, stimuleer wortel- en skietbiomassa-produksie, wortel- en lootlengte en stamwydte in vergelyking met die onbehandelde kontrole groep. Uit die 33308 transkripsies wat geanaliseer is, is 'n totaal van 18.059% gene betekenisvol onderskei tussen die kontrole- en behandelde groepe, waarvan 8.776% geherreguleer is en 9.283% afgereguleer is. Die belangrikste is dat die uitdrukking van gene wat betrokke is by seinttransduksie, stres en proteïenmetabolisme toegeneem het, wat die toename in waargenome groei kan verklaar. Gesamentlik lewer die resultate van hierdie studie bewyse dat BC204 'n groot verandering opwek in 'n verskeidenheid metaboliese prosesse wat deel uitmaak van 'n komplekse netwerk wat 'n breë basisrespons aktiveer. Dit lyk asof hierdie reaksies begin met verbeterde fotosintese, waardeur addisionele energie gekanaliseer kan word na ingewikkelde metaboliese veranderinge deur middel van RNS-regulering en seintransduksie. Baie min metaboliese plantprosesse blykbaar nie deur BC204-behandeling beïnvloed te word nie. | af_ZA |
| dc.description.version | Doctoral | en_ZA |
| dc.embargo.terms | 2021-12-31 | |
| dc.format.extent | xviii, 272 pages : illustrations (some color) | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/109420 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Biostimulants BC204 | en_ZA |
| dc.subject | Plant growth enhancement | en_ZA |
| dc.subject | Arabidopsis thaliana -- Effect of stress on | en_ZA |
| dc.subject | Solanum Lycopersicum | en_ZA |
| dc.subject | Transcriptomic analysis -- Physiological aspects | en_ZA |
| dc.subject | Plants -- Effect of stress on -- Environmental aspects | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Analysis of the molecular and physiological effects following treatment with BC204 in Arabidopsis thaliana and Solanum lycopersicum | en_ZA |
| dc.type | Thesis | en_ZA |