The floral C-lineage Genes Trigger Nectary Development in Petunia and Arabidopsis

First author: Patrice Morel; Affiliations: Ecole Normale Supérieure Lyon (里昂高等师范学院): Lyon, FranceCorresponding author: Michiel Vandenbussche

To attract insects, flowers produce nectar (花蜜), an energy-rich substance (物质) secreted by specialized organs called nectaries. For Arabidopsis thaliana, a rosid species with stamen-associated nectaries, the floral B-, C-, and E- functions were proposed to redundantly regulate nectary development. Here we investigated the molecular basis of carpel-associated nectary development in the asterid species Petunia hybrida (矮牵牛). We show that its euAGAMOUS (euAG) and PLENA (PLE) C-lineage MADS-box proteins are essential for nectary development, while their overexpression is sufficient to induce ectopic nectaries on sepals (萼片). Furthermore, we demonstrate that Arabidopsis nectary development also fully depends on euAG/PLE C-lineage genes. In turn, we show that petunia nectary development depends on two homologs of CRABS CLAW(CRC), a gene previously shown to be required for Arabidopsis nectary development, and demonstrate that CRCexpression in both species depends on the members of both euAG/PLE C-sublineages. Therefore, petunia and Arabidopsis employ a similar molecular mechanism underlying nectary development, despite otherwise major differences in the evolutionary trajectory of their C-lineage genes, their distant phylogeny and different nectary positioning. However, unlike in Arabidopsis, petunia nectary development is position-independent within the flower. Finally, we show that the TARGET OF EAT (TOE)-type BLIND ENHANCER(BEN) and APETALA2 (AP2)-type REPRESSOR OF B-FUNCTION(ROB) genes act as major regulators of nectary size.

为了吸引昆虫，植物的花朵会通过特化器官蜜腺分泌一种富含营养的物质，花蜜。在蔷薇类物种拟南芥中，雄蕊相关的蜜腺的发育是由花B、C、E三大类基因冗余调控的。本文研究了菊类物种矮牵牛中心皮相关的蜜腺的发育分子基础。作者显示矮牵牛中euAG与PLE两个C类MADS-box蛋白对于蜜腺发育十分必要，过表达这两个基因会诱导蜜腺在萼片上异位形成。此外，作者显示拟南芥的蜜腺发育也同样完全依赖于C类基因euAG/PLE。另外，作者的研究显示矮牵牛蜜腺发育依赖于CRC的两个同源基因，CRC基因之前被认为作用于拟南芥的蜜腺发育，并且研究显示CRC在这两个物种中的扩张均依赖于C类基因euAG/PLE。因此，矮牵牛和拟南芥虽然在C类基因上演化轨迹、进化关系及蜜腺位置上存在不同，但两者在蜜腺发育中存在类似的分子机制。然而，与拟南芥不同的是，矮牵牛蜜腺发育依赖于在花中的位置。最终，作者还表明TOE类BEN基因及AP2类ROB基因在蜜腺的大小方面作为主要的调控基因发挥作用。

该研究是里昂高等师范学院Laboratoire Reproduction et Developpement des Plantes中的一个研究方向Evolution and Development of the Flower，该方向主要有两个研究主题，一个是Comparative floral genetics of Petunia hybridaand Arabidopsis thaliana，由Michiel Vandenbussche主导；另一个是The evolution of the carpel in the flowering plants，由Charlie Scutt主导。（详细信息参见官网：http://www.ens-lyon.fr/RDP/spip.php?rubrique4&lang=en）

doi: https://doi.org/10.1105/tpc.18.00425

Journal: Plant Cell

First Published: 07 August, 2018

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