At-MINI ZINC FINGER2 and Sl-INHIBITOR OF MERISTEM ACTIVITY, a Conserved Missing Link in the Regulation of Floral Meristem Termination in Arabidopsis and Tomato

In angiosperms, the gynoecium (雌蕊群) is the last structure to develop within the flower due to the determinate fate of floral meristem (FM; 花分生组织) stem cells. The maintenance of stem cell activity before its arrest (停止) at the stage called FM termination (结束) affects the number of carpels that develop. The necessary inhibition at this stage of WUSCHEL (WUS), which is responsible for stem cell maintenance, involves a two-step mechanism. Direct repression mediated by the MADS-domain transcription factor AGAMOUS (AG), followed by indirect repression requiring the C2H2 zinc-finger protein KNUCKLES (KNU), allow for the complete termination of floral stem cell activity. Here, we show that Arabidopsis thaliana MINI ZINC FINGER2 (AtMIF2) and its homolog in tomato (Solanum lycopersicum), INHIBITOR OF MERISTEM ACTIVITY (SlIMA), participate in the FM termination process by functioning as adaptor proteins (接头蛋白). AtMIF2 and SlIMA recruit AtKNU and SlKNU, respectively, to form a transcriptional repressor complex together with TOPLESS (TPL) and HISTONE DEACETYLASE19 (HDA19). AtMIF2 and SlIMA bind to the WUS and SlWUS loci in the respective plants, leading to their repression. These results provide important insights into the molecular mechanisms governing (FM) termination and highlight the essential role of AtMIF2/SlIMA during this developmental step, which determines carpel number and therefore fruit size.

在被子植物中，因为花分生组织干细胞的命运决定导致雌蕊群是在花中最后发育的一个结构。在花分生组织终止阶段之前干细胞活性的维持会影响发育成心皮的数量。在这个阶段，对于干细胞维持抑制因子WUSCHEL基因的抑制由一个两步的机制所控制。先是由MADS结构域转录因子AG直接抑制，然后再由C2H2锌指蛋白KNU来间接抑制，通过这个两步抑制机制可以完全终止花干细胞的活性。本文现实拟南芥的AtMIF2蛋白和其在西红柿中的同源蛋白SlIMA作为接头蛋白参与了花分生组织的终止。AtMIF2和SlIMA蛋白会各自招募AtKNU和SlKNU，并与TPL和HDA19一起形成转录抑制复合物。AtMIF2和SlIMA会在各自的物种中结合到WUS和SlWUS基因位点上并抑制其表达。本文的结果揭示了花分生组织终止新的分子机制，并突出了AtMIF2/SlIMA在控制心皮数量的发育阶段起到重要作用，并进一步控制果实的大小。

通讯：Frédéric Delmas (https://www6.bordeaux-aquitaine.inra.fr/bfp/Personnel/D-F/Delmas-Frederic)

研究方向：以番茄和草莓等研究肉质果实的花芽、果实发育。

doi: https://doi.org/10.1105/tpc.17.00653