| Abstract |
Significance
IAA carboxyl methyltransferase 1 (IAMT1) converts auxin (IAA) into its methyl ester (MeIAA).
IAMT1
is reportedly critical for shoot development of the nonsymbiotic plant
Arabidopsis
. On the other hand, the function of
IAMT1
in roots is unknown. Here, we found that
IAMT1
is duplicated in the legume lineage, which evolved root nodule symbiosis. In the model legume
Lotus japonicus
, one of two paralogs (named
IAMT1a
) was mainly expressed in root epidermis, but its function is required in the adjacent cell layer, root cortex, where it promotes nodule development. Application of MeIAA, but not IAA, significantly induced
NIN
, a master regulator of nodule development, without rhizobia. These findings illuminate our understanding of intertissue communication acquired during evolution of root nodule symbiosis.
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