Protein engineering and directed evolution are powerful technologies for probing protein sequence-function relationships. These methods have been used to engineer both plant-derived proteins and exogenous proteins heterologously expressed in plants.

In this review, we aim to further increase the interdisciplinary crossover between the disciplines of protein engineering and plant biology by first introducing protein engineering in some detail. This introduction is key to understanding current limitations to protein engineering when applied to plants. Subsequently, we provide an overview of the recent methodological progress in, and novel applications of, protein engineering and directed evolution in plant research.

Protein engineering is the process by which a researcher modifies a protein sequence through substitution, insertion, or deletion of nucleotides in the encoding gene, with the goal of obtaining a modified protein that is more suitable for a particular application or purpose than the unmodified protein.

The focus on application sets protein engineering apart from the broader term “targeted mutagenesis.” Targeted mutagenesis, or site-directed mutagenesis, is a method whereby a specific site within a gene sequence is altered (Hutchison et al., 1978). Such alterations can be performed for engineering purposes, as in protein engineering, or for examining the effect of specific mutations in a gene.