A Tropical Plant’s Heat Resilience and its Fungal Associations in a Changing Climate

Aims: To investigate variation in 1) gene expression in plants that differ in survival after exposure to high temperatures and 2) the plant-fungi relationship across a temperature gradient. Objectives: This research used a non-model system to 1) test for gene expression differences between the sexes and among individuals experiencing periods of high temperature and show differences in heat tolerance, and 2) explore the pattern of variation on plant-fungi relationships across a temperature gradient. Methods: Study species and habitat: Marchantia inflexa, a liverwort, belongs to a group of plants that do not have true vascular tissues (bryophytes). In Trinidad, M. inflexa is found in multiple habitats, including less exposed cool native habitats (streams) and newly colonized more exposed warm habitats (roadsides). We completed substantial research on the species, including mathematical modeling of population dynamics, sex differences in growth, asexual reproduction, physiology, and morphology. In addition, we have genetic resources (a draft DNA sequence (genome) and a gene sequencing study on water stress tolerance). But this rich research history and genetic resources do not directly address M. inflexa responses to increases to heat events or to understand M. inflexa’s relationship with fungi. However, the research history and genetic resources make M. inflexa an ideal system by providing a solid foundation for accomplishing the proposal aims. Objective 1 - Gene expression: We will test for 1) gene expression differences at key points in the heat stress and recovery cycle between male and female plants from two habitats that differ in temperature and 2) gene expression differences between heat-tolerant and heat- sensitive plants. These plants will be selected from among 40 plants collected from the two locations. From each location the most heat-tolerant and most heat-sensitive male and female plants will be used. We will then focus on key genes and to test for their expression levels in other plants from other locations. Objective 2 - Plant-fungus interactions: We will test for variation in the mutualistic relationship between fungus and M. inflexa. We will use at least 10 males and 10 females from 5 locations that differ in temperature. Plants will be collected and returned to the University of Kentucky. Each plant will be divided into two halves. One half will be tested for the presence of fungi with standard staining techniques. In a pilot study we found colonization pattens are consistent with variation in the amount of fungi in plants. We will culture the other half to conduct follow-up investigations on the propensity of the plant and fungi to form a mutualistic relationship across a temperature gradient.