Theses and Dissertations

Issuing Body

Mississippi State University


Li, Jiaxu

Committee Member

Reddy, K. Raja

Committee Member

Klink, Vincent

Committee Member

Popescu, Sorina C.

Date of Degree


Original embargo terms

Visible MSU Only 3 Years

Document Type

Dissertation - Campus Access Only


Molecular Biology

Degree Name

Doctor of Philosophy


College of Agriculture and Life Sciences


Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology


Soybean (Glycine max) and rice (Oryza sativa) are the most important crops cultivated worldwide. The productivity of both crops is severely limited due to drought stresses. Abscisic acid (ABA) signaling is one of the crucial phytohormones which acts as the signaling mediator in different environmental stress for adaptive response of plants. In this study, functional characterization of abscisic acid-activated protein kinase-like kinase 1 (AALK1), and low molecular weight protein tyrosine phosphatase (LMWPTP) were studied by developing gain-ofunction and loss-ofunction phenotypes by transgenesis. Physiological response of AALK1 showed that AALK1 modulates the drought stress response ins soybean plants. The study has demonstrated several key genes are differentially expressed control, and aalk1-RNAi silenced lines under drought treatment. The AALK1 overexpression lines enhanced the transcription of other ABA-responsive genes, indicating that the AALK1 is a positive regulator of ABA-mediated stress signaling pathways in soybean. The phylogenetic analysis and domain analysis also supports that AALK1 is abscisic acid-activated protein kinase and has a role in drought response. Phenotype analysis of LMWPTP in rice showed that transgenic overexpression of LMW-PTP exhibited significantly improved drought tolerance in comparison to RNAi silencing and control plants ,which indicates that LMWPTP modulates the drought stress tolerance of rice plants. Further, 5 putative tyrosine phosphorylated proteins were detected through immunoblotting and identified by mass spectrometry. Some of these tyrosine phosphorylated proteins are likely to be target proteins of LMWPTP. Together, the present findings strengthen the knowledge about the functional role of AALK1 and LMWPTP, which can be utilized as a promising gene-based molecular marker in transgenic breeding for generating crop plants with improved drought tolerance which ultimately improve the grain yields.