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Title:	Transcript profiling of drought-responsive microRNAs in rice at vegetative and reproductive stages
Authors:	Cheah Boon Huat (P63025)
Supervisor:	Kalaivani Nadarajah, Prof. Dr.
Keywords:	RNA Rice -- Drought tolerance Rice -- Effect of drought on Rice -- Genetics Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	9-Nov-2018
Description:	Elucidating the molecular mechanisms of drought response is essential in the effort of breeding drought-tolerant rice. MicroRNAs have emerged as major post-transcriptional regulators in plants against environmental stresses. Hence in this study, the differential expression of microRNAs in five rice lines with different drought tolerance subjected to greenhouse drought or well-watered control conditions were studied at vegetative and reproductive stages via high-throughput sequencing. As a result, two sets of 49 families of rice microRNA were found to be drought-responsive in leaf and stem at vegetative stage respectively with 28 families exhibiting the drought-responsiveness in both tissues. In particular, osa-miR397a/b, osa-miR398b, osa-miR408-5p and osa-miR528-5p were identified as being down-regulated in leaf samples of two drought-tolerant rice varieties while up-regulated in the drought-susceptible variety. Via target gene finding, these microRNAs are related to the control of major biological processes including starch metabolism (osa-miR397a/b targets β-fructofuranosidase), antioxidant defence (osa-miR398b targets copper superoxide dismutases; osa-miR528-5p targets ascorbate oxidase) and respiration (osa-miR398b targets cytochrome c oxidase 5b). Interestingly, they also commonly target copper-containing proteins such as laccases, copper superoxide dismutases and plantacyanin, indicating a connection between copper homeostasis in leaf and drought response, which necessitates additional study. At the reproductive stage, 9 conserved and 34 non-conserved microRNA families were found to be drought-responsive in rice inflorescence with 5 conserved and 30 non-conserved families up-regulated in the drought-tolerant IR87705-7-15-B. The higher number of identified drought-responsive non-conserved microRNAs may suggest their importance over conserved microRNAs in controlling drought response of rice inflorescence. Out of 32 families of inflorescence-specific non-conserved microRNAs observed in expression profiles, 22 families were induced in the IR87705-7-15-B under drought stress. Functional annotation analysis revealed that the target genes of drought-responsive microRNAs identified in IR87705-7-15-B are associated with biological processes such as development, signaling and response to stimulus. Specifically, four inflorescence-specific microRNAs viz. osa-miR5485, osa-miR5487, osa-miR5492 and osa-miR5517, and two non-inflorescence specific microRNAs viz. osa-miR169d and osa-miR169f.2 target genes that are involved in flower or embryonic development. Furthermore, osa-miR169d, osa-miR5492 and osa-miR5517 are implicated in flowering time control. Interestingly, osa-miR2118 and osa-miR2275, which were reported as up-regulated in IR87705-7-15-B but down-regulated in IR77298-14-1-2-10, are involved in the biosynthesis of rice inflorescence-specific small interfering RNAs. The identification of functionally important drought-responsive microRNAs, which are unique to tolerant rice lines and rice developmental stages, are potential to be selected for microRNA-based molecular breeding of drought-tolerant rice.,'Certification of Master's/Doctoral Thesis' is not available,Ph.D.
Pages:	149
Call Number:	QP623.C484 2018 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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