The E subunit of photosystem I is not essential for linear electron flow and photoautotrophic growth in Arabidopsis thaliana.

PSI-E is part of the stromal side of photosystem I (PSI). In Arabidopsis thaliana, the two nuclear genes PsaE1 and PsaE2 code for PSI-E, and transcripts of PsaE1 are markedly more abundant than PsaE2 transcripts. Stable null alleles of the two PsaE genes, psae1-3 and psae2-1, were identified and characterised. The psae2-1 mutant exhibited wild-type like PSI-E abundance and photosynthetic performance, whereas in the psae1-3 mutant PSI-E accumulation was decreased by 85%, together with an impaired thylakoid electron flow and plant growth rate. The psae1-3 psae2-1 double mutant totally lacked PSI-E but was still able to grow photoautotrophically, implying that PSI-E is not essential for PSI accumulation and thylakoid electron flow.