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Role of strigolactones in adventitious rooting of Arabidopsis thaliana callus in vitro
Claassens, Adrianus Petrus. 2024. Role of strigolactones in adventitious rooting of Arabidopsis thaliana callus in vitro. Unpublished doctoral dissertation. Stellenbosch : Stellenbosch University [online]. Available: https://scholar.sun.ac.za/handle/10019.1/131623 Thesis (PhD)--Stellenbosch Univer...
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Stellenbosch : Stellenbosch University
2025
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| access_status_str | Open Access |
| author | Claassens, Adrianus Petrus |
| author2 | Hills, P. N. |
| author_browse | Claassens, Adrianus Petrus Hills, P. N. |
| author_facet | Hills, P. N. Claassens, Adrianus Petrus |
| author_sort | Claassens, Adrianus Petrus |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Claassens, Adrianus Petrus. 2024. Role of strigolactones in adventitious rooting of Arabidopsis thaliana callus in vitro. Unpublished doctoral dissertation. Stellenbosch : Stellenbosch University [online].
Available: https://scholar.sun.ac.za/handle/10019.1/131623
Thesis (PhD)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131623 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:42:59.065Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/131623 Role of strigolactones in adventitious rooting of Arabidopsis thaliana callus in vitro Claassens, Adrianus Petrus Hills, P. N. Kossmann, J. Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics & Institute of Plant Biotechnology. Arabidopsis thaliana -- Roots Phenotype Gene expression Plant cell development Plant hormones -- Development Growth (Plants) Strigolactones -- Mechanism of action UCTD Claassens, Adrianus Petrus. 2024. Role of strigolactones in adventitious rooting of Arabidopsis thaliana callus in vitro. Unpublished doctoral dissertation. Stellenbosch : Stellenbosch University [online]. Available: https://scholar.sun.ac.za/handle/10019.1/131623 Thesis (PhD)--Stellenbosch University, 2024. ENGLISH ABSTRACT: A previous study in the Institute for Plant biotechnology observed that the synthetic strigolactone, GR24, could enhance growth and induce the development of adventitious root-like structures in Arabidopsis callus cultures, despite the considerable body of literature evidence that strigolactones (SL) inhibit adventitious root formation in planta. This study thus aimed to investigate this apparent discrepancy. The first aspect of the study involved a transcriptomic analysis of the effects of GR24 treatment on gene expression of callus cultures, utilising callus derived from Arabidopsis thaliana Columbia-0 wild type (WT) as well as max3 SL biosynthetic mutant and max2 SL perception mutant plants. The second aspect of the project involved physiological growth trials involving the use of specific callus lines derived wild type plants and a variety of SL biosynthetic (max3, max4) and perception (max2, d14) mutants, as well as the purified enantiomers of GR24 (GR245DS and GR24ent5DS). Since the SL and Karrikin (KL) signalling pathways converge at MAX2, a Karrikin-insensitive mutant (kai2) was also included, to distinguish between effects leveraged by these different pathways. To date, no transcriptomic studies have been conducted to determine the effects of GR24 on gene expression in undifferentiated plant cells, which are not under the influence of surrounding organised tissues or plant organs. One particularly interesting observation from this study was the discovery that GR24 can induce gene expression independently of the SL signalling pathway, since a large number of photosynthetic and respiratory genes were differentially expressed in max2 calli following GR24 treatment, possibly via the HY5 light-responsive signalling system. Considering that many recent literature articles investigating the effects of GR24 do not include max2 lines as a control, this SL-perception independent gene expression could suggest that certain conclusions regarding the effects of GR24 may need to be re-evaluated. The transcriptomic study also elucidated that there were only two genes which were consistently up-regulated in the WT and max3 mutants, in a max2-dependent fashion; Kratos (Negative regulator of cell death) and GASA4 (gibberellin responsive gene that can reduce ROS stress damage). Additionally, numerous gene ontologies representing stress metabolism were similarly elucidated in the various treatment groups. This strongly suggested that the rooting phenotype observed in the calli following GR24 treatment was not due to direct stimulation of rhizogenesis, but may rather be due to a rejuvenation effect on the callus. Subsequent physiological growth tests with young callus that had been sub-cultured for less than 3 months and aged callus which had been sub-cultured over a two-year period showed that rhizogenesis is an innate property of young callus when it is transferred to a cytokinin- and auxin-free medium, but that this ability is reduced as the callus ages. However, treatment with GR24 was able to reverse the senescence process, allowing GR24-treated calli to grow more effectively and to produce adventitious roots, in a MAX2-dependent manner. Biochemical analysis of electrolyte membrane leakage and total antioxidant activity (TAC) revealed that both factors were improved in GR24-treated aged calli, but not in young calli, again in a MAX2-dependent fashion. Consequently, this study proposes that GR24 has an antisenescence effect on plant cells and that this is regulated via the classical D14 strigolactone-signalling pathway, possibly mediated via Kratos and GASA4. AFRIKAANSE OPSOMMING: 'n Vorige studie by die Instituut vir Plantbiotegnologie het waargeneem dat die sintetiese strigolaktone, GR24, die groei kan verbeter en die ontwikkeling van adventiewe wortelagtige strukture in Arabidopsis- kalluskulture kan aanmoedig. In die verleke het n aansienlike hoeveelheid literatuur aangedui dat strigolaktone (SL) die vorming van adventiewe wortels in planta inhibeer. Hierdie studie het dus ten doel gehad om hierdie oënskynlike teenstrydigheid te ondersoek. Die eerste aspek van die studie het 'n transkriptomiese analise van die effekte van GR24-behandeling op geenuitdrukking van kalluskulture behels. Dit was met die behulp van kallus afkomstig van Arabidopsis thaliana Columbia-0 wilde tipe (WT), sowel as max3 SL-biosintesemutante en max2 SL-persepsiemutante plante. Die tweede aspek van die projek het fisiologiese groeiproewe behels wat spesifieke kalluslyne gebruik het WT,'n verskeidenheid SL-biosintese- (max3, max4) en SL-persepsie (max2, d14) mutante. Daar was ook gesuiwerde enantiomere van GR24 (GR245DS en GR24ent5DS) gebruik. Aangesien die SL- en Karrikin (KL) seinpaaie by MAX2 saamvloei, is 'n Karrikin-ongevoelige mutant (kai2) ook ingesluit om tussen die effekte wat deur hierdie verskillende paaie bewerkstellig word, te onderskei. Tot op hede is bitter min transkriptomiese studies uitgevoer om die uitwerking van GR24 op geenuitdrukking in ongedifferensieerde plantselle te bepaal, wat nie onder die invloed van omliggende georganiseerde weefsels of plantorgane is nie. Een interessante waarneming uit hierdie studie was die ontdekking dat GR24 geinduseerde geenuitdrukking in max2-lyne onafhanklik van die SL-seinpad n groot aantal fotosintetiese en respirasie-gene andersyds laat uitgedruk. Die is moontlik as gevolg van die HY5 lig-reaktiewe seinstelsel. Inagneminde die feit dat versye onlangse literatuurartikels wat die effekte van GR24 ondersoek, nie max2- lyne as 'n kontrole insluit nie, kan hierdie SL-onafhanklike-persepsie geenuitdrukking daarop dui dat sekere gevolgtrekkings rakende die effekte van GR24 heroorweeg moet word. Die transkriptomiese studie het ook aan die lig gebring dat daar slegs twee gene was wat konstand eweredig opgereguleer is in die WT en max3 mutante, op 'n max2-afhanklike wyse; Kratos (Negatiewe reguleerder van selsterfte) en GASA4 (gibberellien-reaktiewe geen wat ROS-stresskade kan verminder). Boonop is talle geenontologieë wat stresmetabolisme verteenwoordig, op soortgelyke wyse in die verskeie behandelingsgroepe aan die lig gebring. Dit het sterk voorgestel dat die wortelvorming-fenotipe wat waargeneem was in die kallusse na GR24-behandeling nie te wyte was aan direkte stimulasie van wortelforming was nie, maar eerder aan 'n hernuwingseffek op die kallus. Subsekwente fisiologiese groeitoetse met jong kallus wat minder as 3 maande lank gesubkultureer was, en ou kallus wat oor 'n tydperk van twee jaar gesubkultureer was, het getoon dat wortelforming 'n inherente eienskap van jong kallus is wanneer dit na 'n sitokinien- en auksienvrye medium oorgeplaas word. Hierdie vermoë verminder namate die kallus ouer word. Behandeling met GR24 was egter in staat om die verouderingsproses om te keer. Dit het veroorsaak het dat GR24-behandelde kallusse meer effektief kon groei en adventiewe wortels kon produseer, op 'n MAX2-afhanklike wyse. Die biochemiese ondersoek van elektrolietmembraanlekkasie en totale antioksidantaktiwiteit (TAC) het aan die lig gebring dat GR24 behandeling elektrolietmembraanlekkasie verminder en totale antioksidantaktiwiteitskapasiteit vermeerder in ou kallusse, maar dat geen verskil teenwoording is in jong kallusse nie. Die was weer eens op 'n MAX2- afhanklike wyse. Gevolglik stel hierdie studie voor dat GR24 'n anti-verouderingseffek op plantselle het en dat dit gereguleer word deur die klassieke D14 strigolaktone-seinpad, moontlik bemiddel deur Kratos en GASA4. Doctoral 2025-01-29T13:40:03Z 2025-01-29T13:40:03Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131623 en Stellenbosch University 195 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Arabidopsis thaliana -- Roots Phenotype Gene expression Plant cell development Plant hormones -- Development Growth (Plants) Strigolactones -- Mechanism of action UCTD Claassens, Adrianus Petrus Role of strigolactones in adventitious rooting of Arabidopsis thaliana callus in vitro |
| title | Role of strigolactones in adventitious rooting of Arabidopsis thaliana callus in vitro |
| title_full | Role of strigolactones in adventitious rooting of Arabidopsis thaliana callus in vitro |
| title_fullStr | Role of strigolactones in adventitious rooting of Arabidopsis thaliana callus in vitro |
| title_full_unstemmed | Role of strigolactones in adventitious rooting of Arabidopsis thaliana callus in vitro |
| title_short | Role of strigolactones in adventitious rooting of Arabidopsis thaliana callus in vitro |
| title_sort | role of strigolactones in adventitious rooting of arabidopsis thaliana callus in vitro |
| topic | Arabidopsis thaliana -- Roots Phenotype Gene expression Plant cell development Plant hormones -- Development Growth (Plants) Strigolactones -- Mechanism of action UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/131623 |
| work_keys_str_mv | AT claassensadrianuspetrus roleofstrigolactonesinadventitiousrootingofarabidopsisthalianacallusinvitro |