Universität zu Köln

Roggen, Adrian (2022). The role of MIRNA156 and MIRNA157 during floral transition at the shoot apical meristem. PhD thesis, Universität zu Köln.

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Abstract

Developmental transitions are periods of change between phases of greater stability and they enable multicellular organisms to drastically alter their mode of growth. Developmental transitions are subject to strict regulation, often involving small molecules termed microRNAs (miRNAs) that repress target genes posttranscriptionally. In Arabidopsis thaliana (Arabidopsis), miRNA156 controls developmental timing both during vegetative and reproductive growth. Its targets are members of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) family of transcription factors, which includes the floral integrator SPL15 that promotes flowering under non-inductive conditions. Plants expressing miR156-resistant SPL15 (rSPL15) transition prematurely, whereas those that overexpress miR156 are late flowering. In seedlings, miR156 is highly abundant and rapidly decreases as plants grow, thus setting the rate of developmental progression and contributing to the control of flowering time. Two closely related MIR156 and MIR157 families, consisting of eight and four genes respectively, encode isoforms of miR156 in Arabidopsis. Of these, MIR156A, MIR156C, MIR157A and MIR157C are the most abundant and show age-dependent expression patterns. The roles of MIR156 and MIR157 in flowering are often described synonymously and a detailed analysis of their functions during floral transition is currently lacking. Taking advantage of small RNA-sequencing and CRISPR/Cas9- induced mutants, I characterised the relationship among MIR156 and MIR157 genes and their individual contributions towards floral transition. I observed different dynamics in miR156 and miR157 abundance over time that was also reflected in photoperioddependent flowering phenotypes of mutants. Strikingly, mutations in MIR157 genes affected inflorescence development after floral transition, a phenotype that resembled that of rSPL15 plants, but not mir156 mutants. The mechanistic basis for this phenotype was then investigated by performing genetic interaction studies and confocal imaging. The spatial expression pattern of SPL15 and FRUITFULL, which act downstream of miR156, was not altered in mir157 mutants, whereas their temporal expression was accelerated. The combination of mir157 and fruitfull mutations had synergistic effects on inflorescence development.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Roggen, Adrian roggenadrian@gmail.com UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-741868
Date:	2022
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Außeruniversitäre Forschungseinrichtungen > MPI for Plant Breeding Research
Subjects:	Natural sciences and mathematics
Uncontrolled Keywords:	Keywords Language Plant Developmental Biology English Flowering Time English MIRNA156 English MIRNA157 English Shoot Apical Meristem English SQUAMOSA PROMOTER BINDING PROTEIN-LIKE UNSPECIFIED Arabidopsis thaliana UNSPECIFIED
Date of oral exam:	29 November 2022
Referee:	Name Academic Title Coupland, George Prof. Dr. Höcker, Ute Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/74186