Abstract
Photosystem I (PSI) is a primarily target of iron-deficiency in photosynthetic organisms. The decline of functional PSI by iron deficiency affects the balance of electron transfer from photosystem II (PSII) to PSI. In young leaves of barley, iron-deficiency induced the high thermal dissipation (NPQ) which was mediated by major light-harvesting antenna of PSII, Lhcb1. To evaluate the role of Lhcb1 protein in the barley leaves, we investigated the behavior of Lhcb1 in the isolated thylakoid membranes. Results showed that relatively high amount of Lhcb1 were in monomeric form and were present in the stroma-exposed membrane as well as grana membrane under iron-deficiency. Fluorescence spectra determined at 77K revealed that a peak around 740 nm derived from PSI complex was slightly blue-shifted under the condition of iron-deficiency. These results indicated that migrated Lhcb1 from PSII to PSI might be not simply docking to the lateral side of PSI complex, although the mobile pool of monomeric Lhcb1 increased and appeared to be in the quenched form in iron-deficient leaves.
