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

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Abstract
Changes induced by arbuscular mycorrhizal (AM) formation in the plasma membrane polypeptide pattern of tomato roots have been assessed by 2D‐PAGE analysis. Plasma membrane fractions were isolated by aqueous two‐phase partitioning from control and mycorrhizal tomato root microsomes. Analysis of 2D‐PAGE gels revealed that AM colonization induces at the plasma membrane level two major changes in protein synthesis: down‐regulation of some constitutive polypeptides and synthesis of new polypeptides or endomycorrhizins. A comparison of changes induced by two different levels of AM colonization showed that 16 polypeptides were differentially displayed at both AM colonization stages, while some others were transiently regulated. Five of the differentially displayed plasma membrane polypeptides at both AM colonization stages were selected for N‐terminal amino acid sequencing. Reliable sequences were obtained for two of the selected spots. Sequence alignment search indicated that one of the sequenced polypeptides showed 75% identity to the N‐terminal sequence of the 69 kDa catalytic subunit of the vacuolar type H+‐ATPase of several plants. The possible significance of these findings is discussed in relation to the functioning of the AM symbiosis.