Investigating the role of hormones during drought and desiccation tolerance in two evolutionarily distant resurrection plants.

Kirchner, S.*

University of Cape Town

The term 'resurrection plants' refers to a specialized group of angiosperm species capable of surviving severe dehydration, down to <95% relative water content. In the past, significant advances in the field of molecular biology has allowed for an ever-growing understanding into the molecular mechanisms inherent in granting desiccation tolerance in these plants. Although hormones play a crucial role in the regulation of many molecular pathways associated with desiccation tolerance in drought-sensitive angiosperms, very little research has been dedicated to understanding the many functions of hormones in resurrection plants. Thus this research aims to examine the desiccation-affiliated hormone profiles and additional gene expression patterns of two evolutionarily distant resurrection plants, namely Xerophyta schlecteri and Craterostigma pumilum. Leaf and root tissues were sampled at time points corresponding to full turgor, ~80%, ~60%, ~20% and air dry relative water content (RWC) states to assess similarities and differences between hormone abundance during drought stress. Additionally, this research aims to investigate the existence of an auxin gradient in the leaves of Craterostigma pumilum as proposed by du Toit et al. (2022) and its potential assistance in the conference of desiccation tolerance. Due to the complex nature of hormone crosstalk and signalling pathways, particular attention is also required towards understanding individual cascade pathways and the ways in which they are affected by direct and indirect hormone interactions. Therefore, following hormone analyses, this research also focuses specifically on gene expression patterns in the jasmonic acid pathway and the potential relationship between three potential genes of interest; MYC2, GASA3 and RD29B, and relevant hormone interactions during desiccation. Thus far, hormone identification of major hormone classes including GA, ABA, JA, SA and OPDA, was conducted using HPLC-ESI-MS/MS, with tentative results suggesting that potential significant differences exist between hormone expression within the leaves and roots of both species at different time points, as well as generally between the species themselves. There is also evidence to suggest a degree of translocation of certain hormones between the different tissue types.