Alterations in the plasma membrane polypeptide pattern of tomato roots (Lycopersicon esculentum) during the development of arbuscular mycorrhiza

Changes induced by arbuscular mycorrhizal (AM) formation in the plasma memb rane polypeptide pattern of tomato roots have been assessed by SD-PAGE anal ysis. Plasma membrane fractions were isolated by aqueous two-phase partitio ning from control and mycorrhizal tomato root microsomes. Analysis of PD-PA GE gels revealed that AM colonization induces at the plasma membrane level two major changes in protein synthesis: down-regulation of some constitutiv e polypeptides and synthesis of new polypeptides or endomycorrhizins. A com parison of changes induced by two different levels of AM colonization showe d that 16 polypeptides were differentially displayed at both AM colonizatio n stages, while some others were transiently regulated. Five of the differe ntially displayed plasma membrane polypeptides at both AM colonization stag es were selected for N-terminal amino acid sequencing. Reliable sequences w ere obtained for two of the selected spots. Sequence alignment search indic ated that one of the sequenced polypeptides showed 75% identity to the N-te rminal sequence of the 69 kDa catalytic subunit of the vacuolar type H+-ATP ase of several plants. The possible significance of these findings is discu ssed in relation to the functioning of the AM symbiosis.