Date of Award
Doctor of Philosophy (PhD)
Biotic and abiotic stress factors consistently threaten during different stages of the plant’s life cycle. A complex network of signaling molecules is required to overcome stresses, which is linked to general physiological and molecular processes. Botrytis cinerea is a necrotrophic fungal pathogen that causes grey mold disease on many crops. Apart from B. cinerea, several biotic, abiotic, and hormonal stresses have detrimental effects on plant growth and productivity. The aim of this study is to identify the genetic regulations of individual stress types using comparative microarray analyses, and to find out the role of differentially expressed genes in Arabidopsis-B. Cinerea pathosystem and the common genetic regulations across these stresses in response to B. cinerea. The transcriptomic data were analyzed to identify the overlapping stress-regulated genes in response to B. cinerea and other biotic (Alternaria brassicicola, Pseudomonas syringae PV tomato DC3000 and DC3000 avrRpm1, and Peris rape), abiotic (oxidative stress and wounding) and hormonal (salicylic acid, methyl jasmonate, ethylene and abscisic acid) stresses. Among the 1554 B. cinerea up-regulated genes, 24%, 1.4%, and 14% were commonly induced by biotic, abiotic, and hormonal treatments respectively. Similarly, about 18%, 2.5%, and 22% of B. cinerea down-regulated genes were commonly repressed by these stress groups. WRKY33 transcription factor was previously reported for its resistance to B. cinerea. In this study, Arabidopsis WRKY33 over-expression and mutant lines were compared for their response to B. cinerea infection. The wrky33 mutant plants showed altered susceptibility, whereas the 35S: WRKY33 overexpression plants showed resistance to B. cinerea. The expression profile of 12-oxo-phytodienoic acid and phytoprostane A1-treated Arabidopsis plants in response to B. cinerea showed that cyclopentenones can also modulate WRKY33 regulation upon inoculation with B. cinerea. These results support the role of electrophilic oxylipins in mediating plant responses to B. cinerea infection through the TGA transcription factor. Results obtained from the metatranscriptomic and in silico gene analyses revealed the involvement of RAP2.4 (related to AP2.4) in plant immunity. Arabidopsis rap 2.4 T-DNA insertion mutant lines exhibited increased resistance to B. cinerea. This is the first report to uncover the role of RAP2.4 in plant defense against B. cinerea. This will pave the way for producing crops with less use of chemical pesticides and will provide a basis for breeding programs to increase tolerance and improve yield performance in crops.
Valiyaveettil Shamgopal, Arjun Sham, "Expression Profiling and Mutant Analysis Reveal Complex Regulatory Networks Involved In Arabidopsis Response to Biotic, Abiotic and Hormonal Stresses" (2020). Philosophy Dissertations. 11.