The CESA gene family in seed plants is characterized by six major clades of isoforms, including three typically required for primary wall cellulose synthesis (by reference to Arabidopsis thaliana, AtCESA1,3,6 or 6-like isoforms) and three typically required for secondary wall cellulose synthesis (AtCESA4,7,8). In some species, there is more than one CESA isoform within one or more clades: for example, 15 CESAs exist in a diploid cotton species (Gossypium raimondii). The CESAs of the moss Physcomitrella patens exist in two other distinct clades as compared to the seed plants, each one reflecting specialized functions in this descendant of early-evolved land plants. We know little about any potential biochemical differences between the plant CESA isoforms. The existence of distinct clades could merely represent accidentally-evolved position requirements within the multimeric cellulose synthesis complex as a result of random mutations within separate protein lineages. Previously, we analyzed the effects of several analogous mutations in PpCESA5 and AtCESA1 protein regions that may impact substrate access and coordination in the active site, as inferred from a bacterial cellulose synthase with a solved structure. Complementation of the respective mutants showed more severe impacts for sequence changes in this region for AtCESA1 in this bryophyte/seed plant comparison. We will report the results of extending this analysis to AtCESA7, another seed plant CESA, and discuss the current overall understanding of functional differences between CESA isoforms.

Mutation analysis to explore potential functional differences among plant CESA isoforms

255th National Meeting (2018)

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