Acquisition and diversification of tendrilled leaves in B ignonieae ( B ignoniaceae) involved changes in expression patterns of SHOOTMERISTEMLESS ( STM ), LEAFY/FLORICAULA ( LFY / FLO ), and PHANTASTICA ( PHAN )

Summary Leaves have undergone structural modifications over evolutionary time, and presently exist in many forms. For instance, in F abaceae and B ignoniaceae, leaf parts can be modified into tendrils. Currently, no data are available on genic control of tendrilled leaf development outside Fabaceae. Here, we conducted a detailed study of three representatives of B ignonieae: A mphilophium buccinatorium , D olichandra unguis‐cati , and B ignonia callistegioides , bearing multifid, trifid, and simple‐tendrilled leaves, respectively. We investigated the structure of their petioles, petiolules, leaflets, and tendrils through histological analyses. Additionally, the expression of SHOOTMERISTEMLESS ( STM ), PHANTASTICA ( PHAN ), and LEAFY/FLORICAULA ( LFY / FLO ) during leaf development was analyzed by in situ hybridizations. Tendrils share some anatomical similarities with leaflets, but not with other leaf parts. Transcripts of both STM and LFY / FLO were detected in leaf primordia, associated with regions from which leaflets and tendril branches originate. PHAN expression was found to be polarized in branched tendrils, but not in simple tendrils. In B ignonieae, tendrils are modified leaflets that, as a result of premature completion of development, become bladeless organs. Bignonieae leaves develop differently from those of peas, as both LFY / FLO and STM are expressed in developing leaves of B ignonieae. Moreover, PHAN is probably involved in tendril diversification in B ignonieae, as it has distinct expression patterns in different leaf types.