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K-State Today

April 4, 2019

Division of Biology Seminar April 5

Submitted by Division of Biology

Prachee Avasthi, assistant professor at the University of Kansas Medical Center, will present "Significant Functional Overlap of Divergent Actin Isoforms in the Unicellular Green Alga Chlamydomonas Reinhardtii" as part of the Division of Biology Seminar Series at 4 p.m. Friday, April 5, in 221 Ackert Hall.

Avasthi will lecture on varieties of organisms that express multiple actin isoforms encoded by different genes, which are sometimes tissue specific or developmentally regulated. However, the selective localization and
segregation of cytoskeletal functions of these genes are understudied. Here we consider two actins found in the genome of the green alga Chlamydomonas reinhardtii, which share ~63% sequence identity: the conventional actin IDA5 and the divergent actin NAP1. The behavior and functions of these actins have been underexplored due to the difficulty in visualizing filaments with traditional methods and mild phenotypes seen in null mutants of these genes. Through adjusted fluorescence protocols and in situ cryo electron tomography, we are now able to visualize filaments of these actin polymers near the nuclear envelope, ER, and Golgi apparatus.

We also find a significant amount of functional redundancy between IDA5 and NAP1, particularly in the growth of motile flagella in these cells. Either IDA5 or NAP1 expression is an absolute requirement for flagellar assembly from newly synthesized proteins, likely due to a role in transport of Golgi-adjacent vesicles during assembly. Flagellar protein synthesis at normal levels also requires one form of actin during flagellar assembly. Finally, these actins are required for protein organization of the region essential for gating at the base of flagella called the transition zone. Ultimately, IDA5 appears to be able to perform all of the identified functions of NAP1 with equal efficiency, but not vice versa. These experiments provide broader insight into the behaviors of multiple actin isoforms within a single cell.

If you would like to visit with Avasthi, please contact Steph Shames at sshames@k-state.edu