Acquisition and diversification of tendrilled leaves in Bignonieae(Bignoniaceae) involved changes in expression patterns ofSHOOTMERISTEMLESS (STM), LEAFY/FLORICAULA (LFY/FLO), and PHANTASTICA (PHAN)

摘要

Leaves have undergone structural modifications over evolutionary time, and presently existin many forms. For instance, in Fabaceae and Bignoniaceae, leaf parts can be modified intotendrils. Currently, no data are available on genic control of tendrilled leaf developmentoutside Fabaceae. Here, we conducted a detailed study of three representatives of Bignonieae:Amphilophium buccinatorium, Dolichandra unguis-cati, and Bignonia callistegioides, bearingmultifid, trifid, and simple-tendrilled leaves, respectively. We investigated the structure oftheir petioles, petiolules, leaflets, and tendrils through histological analyses. Additionally, theexpression 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. Transcriptsof both STM and LFY/FLO were detected in leaf primordia, associated with regionsfrom which leaflets and tendril branches originate. PHAN expression was found to be polarizedin branched tendrils, but not in simple tendrils. In Bignonieae, tendrils are modified leaflets that, as a result of premature completion ofdevelopment, become bladeless organs. Bignonieae leaves develop differently from those ofpeas, as both LFY/FLO and STM are expressed in developing leaves of Bignonieae. Moreover,PHAN is probably involved in tendril diversification in Bignonieae, as it has distinct expressionpatterns in different leaf types.