Generation and characterization of single and multigene Arabidopsis thaliana mutants in LSU1-4 (RESPONSE TO LOW SULFUR) genes.

In Arabidopsis thaliana, there are four members of the LSU (RESPONSE TO LOW SULFUR) gene family which are tandemly located on chromosomes 3 (LSU1 and LSU3) and 5 (LSU2 and LSU4). The LSU proteins are small, with coiled-coil structures, and they are able to form homo- and heterodimers. LSUs are involved in plant responses to environmental challenges, such as sulfur deficiency, and plant immune responses. Assessment of the role and function of these proteins was challenging due to the absence of deletion mutants. Our work fulfills this gap through the construction of a set of LSU deletion mutants (single, double, triple, and quadruple) by CRISPR/Cas9 technology. The genomic deletion regions in the obtained lines were mapped and the level of expression of each LSUs was assayed in each mutant. All lines were viable and capable of seed production. Their growth and development were compared at several different stages with the wild-type. No significant and consistent differences in seedlings' growth and plant development were observed in the optimal conditions. In sulfur deficiency, the roots of 12-day-old wild-type seedlings exhibited increased length compared to optimal conditions; however, this difference in root length was not observed in the majority of lsu-KO mutants.