Publications

Functional copy number variation in SQUALENE EPOXIDASE-LIKE genes affects photosystem II efficiency in Arabidopsis

van Bezouw, R.F.H.M.; Nguyen, T.P.; van Hoang, N.; Vincenzi, E.; van Velthoven, Rosanne; Zhang, Hui; Gao, Yan; Zhang, W.; Jacobi, Renze; de Snoo, Bastiaan; Reyes Marquez, F.C.; Vazquez Catalá, Livia; Iqbal, M.; Jansen, S.; Mumm, R.; Harbinson, J.; Keurentjes, J.J.B.; Aarts, M.G.M.

Summary

In this study, we found a single quantitative trait locus for photosystem II efficiency (ΦPSII) in the Arabidopsis Ler-0 x Col-0 recombinant inbred line population. This locus on chromosome 5 is caused by genetic variation in a cluster of tandemly repeated SQUALENE EPOXIDASE-LIKE (SQE-like) genes, with unknown function. We show the QTL is caused by variation in the SQE5, SQE6 and SQE7 genes affecting ΦPSII in a dose-dependent manner, due to a combination of functional copies. Col-0 carries only one functional copy, SQE5, while Ler-0 carries functional copies of SQE6 and SQE7. Overexpression of a functional copy of SQE6 enhances ΦPSII to exceed that of the Ler-0 parent in Arabidopsis, but does not affect ΦPSII in tobacco. Phylogenetic analysis of the SQE and SQE-likes in 135 plant species revealed that the SQE-likes are evolutionary confined to two sister families, the Cleomaceae and Brassicaceae, and diversified independently. The tandem cluster of four SQE-like genes in Arabidopsis is likely the result of two recent gene duplication events, one generating SQE5 from SQE4, the next one generating SQE6 and SQE7 from SQE5. The involvement of SQE-like genes in photosynthesis will open up new avenues to determine the function of these novel genes.