Triggered Pluripotency During Kalanchoë Plantlet Development

Abstract

In contrast to animal cells, plant cells demonstrate incredible plasticity in terms of cell fate changes. A differentiated plant cell can be triggered to de-differentiate and regain its pluripotency. Kalanchoë plants evolved to have a distinctive asexual reproductive strategy by forming plantlets, miniature versions of adult plant on the leaf margin. Previous studies have shown that plantlet formation in Kalanchoë daigremontiana involves the process of ectopic embryogenesis, in which differentiated leaf cells de-differentiate and regain totipotent potential to develop into an embryo. However, molecular mechanism(s) underlying this cell fate change during plantlet formation remains elusive. This project aims to uncover genetic mechanisms and hormonal control of plantlet formation through expression analyses of candidate genes, phenotype analyses of transgenic plants and RNA-sequencing analysis. It was found that a late embryogenesis gene, FUSCA3 has the potential to replace embryogenesis functions of LEAFY COTYLEDON 1 needed for K. daigremontiana plantlet formation. In addition, two key meristem genes, WUSCHEL and CLAVATA1 were required for plantlet formation as these genes were expressed during plantlet development and reduced expression of these genes affected plantlet number and morphology. Auxin was also involved in regulating plantlet formation. Changes in expression of an auxin biosynthesis enzyme gene YUCCA1 were in seen in transgenic plants with reduced plantlets, and the auxin efflux transporter PIN1 was present at the leaf notches prior to pedestal and plantlet formation. Furthermore, a complex auxin-cytokinin crosstalk might be involved in regulating plantlet formation as plants with reduced expression of a putative cytokinin signalling inhibitor, KdaHP, exhibited irregular plantlet formation and was also accompanied by changes in YUCCA1 expression. Moreover, KdaHP was highly expressed during wild-type plantlet development and novel cytokinin activity was observed during early plantlet formation. K. daigremontiana forms plantlets constitutively whereas K. pinnata forms plantlets only upon stress induction. RNA-sequencing showed that there were more unique than shared biological processes involved in regulating K. daigremontiana and K. pinnata plantlet formation. Although further studies are required, this work has illustrated novel insights into the molecular mechanisms of plantlet formation. Transcriptome analysis of Kalanchoë plantlet formation and molecular experiments presented in this study will be pioneering sources of information for future studies on plant triggered pluripotency and developmental plasticity.

Date of Award	1 Aug 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Giles Johnson (Supervisor) & Minsung Kim (Supervisor)