Natural and targeted isovariants of the rice actin depolymerizing factor 2 can alter its functional and regulatory binding properties

Authors: SENGUPTA, SONALI - Louisiana State University Agcenter; Rajasekaran, Kanniah - Rajah; BAISAKH, NIRANJAN - Louisiana State University Agcenter

Submitted to: Biochemical and Biophysical Research Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2018
Publication Date: 7/19/2018
Citation: Sengupta, S., Rajasekaran, K., Baisakh, N. 2018. Natural and targeted isovariants of the rice actin depolymerizing factor 2 can alter its functional and regulatory binding properties. Biochemical and Biophysical Research Communications. 503:1516-1523. https://doi.org/10.1016/j.bbrc.2018.07.073.
DOI: https://doi.org/10.1016/j.bbrc.2018.07.073

Interpretive Summary: The protein family called Actin depolymerizing Factors (ADF) affects cell division and elongation in higher plants, and are involved in molecular signaling related to stress response and defense mechanism against microbial attack. In this manuscript, we analyzed biochemical difference between rice ADF2 and its salt/drought-resistant relative in the Louisiana marshgrass. The differences in ADF2 protein between the two plants were only six amino acids. Based on the amino acid differences, targeted single amino acid mutations of rice ADF2 were created and the biochemical properties and structural changes were studied. The findings suggest that a single mutation in ADF2 could change the structure-function relationship and alter the actin binding efficiency resulting in changes in regulatory functions governing stress caused by salt, drought or microbes. This study helps to understand the effectiveness of genetic manipulation through gene-editing to improve stress and disease tolerance. The results presented in this study is useful to other plant biotechnologists to develop stress or disease-tolerant crops.

Technical Abstract: Actin depolymerizing factors (ADFs) are ubiquitous actin-binding proteins that play essential roles in maintaining cellular actin dynamics by depolymerizing/severing F-actin. Plant ADF isoforms show functional divergence via differential biochemical and cellular properties. We have shown previously that ADF2 of rice (OsADF2) and smooth cordgrass (SaADF2) displayed contrasting biochemical properties and stress response variance in planta. As a proof-of-concept that amino acid variances contribute to such functional difference, single amino acid mutants of OsADF2 were generated based on its sequence differences with SaADF2. Biochemical studies showed that the single-site amino acid mutations altered actin binding, depolymerizing, and severing properties of OsADF2. Phosphosensitive mutations, such as serine-6>threonine, changed the regulatory phosphorylation efficiency of ADF2 variants. The N-terminal mutations had greater effect on the phosphorylation pattern of OsADF2, whereas C-terminal mutations affected actin binding and severing. The presence of introduced mutations in isovariants of monocot ADF suggests that these residues are significant control points regulating their functional divergence, including abiotic stress response.