PhD Oral Exam - Pooja Kaushik, Biology

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

As the global population grows and water scarcity becomes more pressing, improving photosynthetic efficiency and reducing crop losses due to drought stress are critical challenges for modern agriculture. This PhD research addresses these challenges by investigating stomatal development, drought stress tolerance, and chloroplast biogenesis in plants. The primary objectives of the research were to identify epidermal patterning factors (EPF) signaling peptides involved in stomatal development in Brachypodium distachyon, explore the role of Arabidopsis thaliana EPFL1, EPFL2, and EPFL3 genes in drought tolerance, and finally, investigate the roles of Arabidopsis Mitogen activated protein kinase (MAPK) phosphatases (MKP2 and DsPTP1) in chloroplast biogenesis. The findings revealed that Brachypodium EPF peptides (BdEPFL1-1, BdEPFL2-2, BdEPFL6-1, and BdEPFL6-2 play a role in stomatal patterning, with overexpression leading to reduced stomatal density, validated through complementation studies in Arabidopsis. In the drought tolerance study, overexpression of EPFL1 significantly enhanced drought resistance in an ABA-dependent manner, whereas EPFL2 worked in an ABA-independent manner, highlighting distinct regulatory pathways for these genes. The final part of this research focused on the roles of MAPK phosphatases MKP2 and DsPTP1 in regulating chloroplast biogenesis. Mutant analyses showed that the absence of these phosphatases resulted in impaired chloroplast development, stunted growth, and an albino phenotype, revealing their role as negative regulators of chloroplast formation. Higher order mutants with mutations in MAPKs revealed their likely downstream targets. These findings offer significant insights into plant development, with implications for enhancing crop resilience and photosynthesis in response to global climate challenges.