The bHLH transcription factor SPATULA enables cytokinin signaling, and both activate auxin biosynthesis and transport genes at the medial domain of the gynoecium.
The bHLH transcription factor SPATULA enables cytokinin signaling, and both activate auxin biosynthesis and transport genes at the medial domain of the gynoecium.
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DOI：
10.1371/journal.pgen.1006726
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发表时间：
2017-04
期刊：
影响因子：
4.5
通讯作者：
de Folter S
中科院分区：
文献类型：
--
作者：
Reyes-Olalde JI;Zúñiga-Mayo VM;Serwatowska J;Chavez Montes RA;Lozano-Sotomayor P;Herrera-Ubaldo H;Gonzalez-Aguilera KL;Ballester P;Ripoll JJ;Ezquer I;Paolo D;Heyl A;Colombo L;Yanofsky MF;Ferrandiz C;Marsch-Martínez N;de Folter S
水果和种子是地球上的主要食物来源。这两种器官都来自雌蕊，因此，了解引导这一器官在被子植物物种中发育的机制至关重要。在拟南芥中，雌蕊由两个天生融合的心皮组成，其中可以区分两个域：内侧和外侧。内侧区域包括心皮边缘分生组织（CMM），它是产生参与受精的内部组织的关键，如隔膜、胚珠和传递道。有趣的是，内侧区域显示出高的细胞分裂素信号输出，而外侧区域几乎检测不到。虽然已知细胞分裂素提供分生组织特性，但对年轻雌蕊中细胞分裂素信号模式的机制尚缺乏了解。此外，在其他组织中，细胞分裂素途径通常与生长素途径相连，但我们对年轻雌蕊中的这些联系也缺乏了解。我们的研究结果表明，细胞分裂素信号可以提供CMM活性和生长所需的分生组织特性，它是由转录因子SPATULA （SPT）在中间区域激活的。同时，细胞分裂素信号被细胞分裂素反应抑制因子拟南芥组氨酸磷酸转移酶6 （AHP6）限制在内侧区域，也可能被ARR16 （a型ARR）限制，两者都存在于发育中的雌核的外侧区域（假定的瓣膜）。此外，SPT和细胞分裂素可能共同促进拟南芥生长素生物合成基因色氨酸氨基转移酶1 （TAA1）和编码生长素外排转运蛋白PIN-FORMED 3 （PIN3）的基因的表达，可能产生对雌蕊生长重要的生长素分泌。本研究为年轻雌蕊细胞分裂素信号模式的时空测定及其与生长素通路的联系提供了新的见解。我们的大部分食物来自于水果和种子，它们来自于受精的雌蕊。因此，了解控制雌蕊发育的机制至关重要。拟南芥雌蕊有两个融合的心皮，中间有一个心皮区，外侧有一个心皮壁区。所有参与生殖的组织都起源于中部的心皮边缘分生组织。植物激素细胞分裂素为细胞提供分生组织活性，有趣的是，在年轻的雌蕊中，内侧而不是外侧区域呈现强烈的细胞分裂素信号传导。我想到的一个问题是如何定义这种模式。这项工作表明，转录因子SPATULA使细胞分裂素信号传导在内侧区域，而细胞分裂素信号传导抑制因子存在于外侧区域。第二个问题是细胞分裂素是否以及如何与生长素（一种组织分化的重要植物激素）沟通。我们发现细胞分裂素和SPT激活生长素的生物合成和转运基因。这些发现的整合提供了第一个基因调控网络在早期雌蕊发育过程中起作用。这个网络最有可能在开花植物中保守，并且可以提供对食物生产至关重要的分子过程的见解。
Fruits and seeds are the major food source on earth. Both derive from the gynoecium and, therefore, it is crucial to understand the mechanisms that guide the development of this organ of angiosperm species. In Arabidopsis, the gynoecium is composed of two congenitally fused carpels, where two domains: medial and lateral, can be distinguished. The medial domain includes the carpel margin meristem (CMM) that is key for the production of the internal tissues involved in fertilization, such as septum, ovules, and transmitting tract. Interestingly, the medial domain shows a high cytokinin signaling output, in contrast to the lateral domain, where it is hardly detected. While it is known that cytokinin provides meristematic properties, understanding on the mechanisms that underlie the cytokinin signaling pattern in the young gynoecium is lacking. Moreover, in other tissues, the cytokinin pathway is often connected to the auxin pathway, but we also lack knowledge about these connections in the young gynoecium. Our results reveal that cytokinin signaling, that can provide meristematic properties required for CMM activity and growth, is enabled by the transcription factor SPATULA (SPT) in the medial domain. Meanwhile, cytokinin signaling is confined to the medial domain by the cytokinin response repressor ARABIDOPSIS HISTIDINE PHOSPHOTRANSFERASE 6 (AHP6), and perhaps by ARR16 (a type-A ARR) as well, both present in the lateral domains (presumptive valves) of the developing gynoecia. Moreover, SPT and cytokinin, probably together, promote the expression of the auxin biosynthetic gene TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS 1 (TAA1) and the gene encoding the auxin efflux transporter PIN-FORMED 3 (PIN3), likely creating auxin drainage important for gynoecium growth. This study provides novel insights in the spatiotemporal determination of the cytokinin signaling pattern and its connection to the auxin pathway in the young gynoecium. Most of our food comes from fruits and seeds, derived from a fertilized gynoecium. Therefore, understanding the mechanisms that control gynoecium development is of crucial importance. The Arabidopsis gynoecium has two fused carpels, with a medial domain between them, and a lateral domain consisting of the carpel walls. All the tissues that are involved in reproduction arise from the carpel margin meristem in the medial domain. The phytohormone cytokinin provides meristematic activity to cells, and interestingly, in a young gynoecium, the medial, but not the lateral, domain presents strong cytokinin signaling. One question that comes to mind is how this pattern is defined. This work demonstrates that the transcription factor SPATULA enables cytokinin signaling at the medial domain, while cytokinin signaling repressors are present in the lateral domain. A second question is whether and how cytokinin in the medial domain communicates with auxin, an important phytohormone for tissue differentiation. We found that cytokinin and SPT activate auxin biosynthesis and transport genes. The integration of these findings gives the first gene regulatory network acting during early gynoecium development. This network is most likely conserved in flowering plants, and can provide insights of molecular processes that are key for food production.