Maternal auxin supply contributes to early embryo patterning in Arabidopsis

First author: Hélène S. Robert; Affiliations: Masaryk University (马萨里克大学): Brno, Czech Republic

Corresponding author: Hélène S. Robert

The angiosperm seed is composed of three genetically distinct tissues: the diploid embryo that originates from the fertilized egg cell (受精卵细胞), the triploid endosperm that is produced from the fertilized central cell (中央细胞), and the maternal sporophytic integuments (珠被) that develop into the seed coat (种皮). At the onset of embryo development in Arabidopsis thaliana, the zygote (合子) divides asymmetrically (不对称地), producing a small apical embryonic cell and a larger basal cell that connects the embryo to the maternal tissue. The coordinated and synchronous (同步的) development of the embryo and the surrounding integuments, and the alignment of their growth axes, suggest communication between maternal tissues and the embryo. In contrast to animals, however, where a network of maternal factors that direct embryo patterning have been identified, only a few maternal mutations have been described to affect embryo development in plants. Early embryo patterning in Arabidopsisrequires accumulation of the phytohormone auxin in the apical cell by directed transport from the suspensor (胚柄). However, the origin of this auxin has remained obscure. Here we investigate the source of auxin for early embryogenesis and provide evidence that the mother plant coordinates seed development by supplying auxin to the early embryo from the integuments of the ovule (胚珠). We show that auxin response increases in ovules after fertilization, due to upregulated auxin biosynthesis in the integuments, and this maternally produced auxin is required for correct embryo development.

被子植物的种子由三个遗传组成不同的组织构成：一是由受精卵细胞发育而成的二倍体胚；二是由受精中央细胞发育而成的三倍体胚乳；三是由母本珠被组织发育而成的种皮。在拟南芥胚胎发育起始，合子会不对称分裂，形成一个稍小的顶端胚细胞和一个稍大的基细胞，后者将胚与母本的组织相连。胚与周围母本组织的同步协调发育及生长轴的配对，说明母本组织与胚之间存在某种联系。与动物中已经鉴定了母本因子组成的网络直接调控胚发育模式不同，植物中很少有母本突变影响胚胎发育。从胚柄运输而来的顶细胞中生长素的积累对于拟南芥胚胎早期发育十分重要。然而，生长素的来源还不清楚。本文研究了早期胚胎发育中的生长素来源，结果显示母本胚珠的珠被组织通过向早期胚胎发育提供生长素调控种子发育。作者的研究显示胚珠中的生长素响应在受精作用后增强，这是由于珠被中生长素生物合成的上调所导致的，这种母本所产生的生长素对于胚胎的正常发育至关重要。

通讯：Hélène S. Robert (https://www.muni.cz/en/people/119675-helene-robert-boisivon)

doi: https://doi.org/10.1038/s41477-018-0204-z

Journal: Nature Plants

Published date: 16 July, 2018

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