Potassium channel AtTPK5 : An essential or redundant regulator of photosynthesis in Arabidopsis?

Abstract: It has previously been stated that K+-ions in a plant cell have a counter-balancing role in which the efflux of K+-ions from the thylakoid lumen charge-balance the light-induced proton pumping that is known to occur across the thylakoid membrane, and this in turn stabilizes photosynthetic activity. In the present study, two different types of plants of the same ecotype (Col-0) of Arabidopsis thaliana have been studied: a wild-type and a T-DNA exon-mutant (tpk5-e) that has lost the expression of the protein known as Tandem-pore K+- channel (AtTPK5). The plants were grown in a hydroponic system under normal light conditions with 70% humidity. Homozygous (HM) tpk5-e mutant plants were screened using PCR and gene specific primers. Further, the photosynthetic activity was measured in 4 hour light-adapted plants and the photosynthetic activity of the tpk5-e mutant proved not to be significantly different in comparison to the wild-type when measuring the electron transport rate (ETR). Furthermore, the O2-evolution was also measured in 4 hour light-adapted plants and the tpk5-e mutant's O2-evolution proved to be significantly lower in the tpk5-e mutant in comparison to the wild-type under high light conditions. The plant fitness of the wild-type and tpk5-e mutant was also different judging from phenotypic traits such as chlorophyll expression. However, the measured chlorophyll amount of pigments chlorophyll a and b proved not to be significantly different in the tpk5-e mutant in comparison to the wild-type.