Growth dynamics of the Arabidopsis fruit is mediated by cell expansion

First author: Juan-José Ripoll; Affiliations: University of California, San Diego (加州大学圣地亚哥分校): La Jolla, USA

Corresponding author: Adrienne H. K. Roeder

Fruit have evolved a sophisticated tissue and cellular architecture to secure plant reproductive success. Postfertilization growth is perhaps the most dramatic event during fruit morphogenesis. Several studies have proposed that fertilized ovules and developing seeds initiate signaling cascades to coordinate and promote the growth of the accompanying fruit tissues. This dynamic process allows the fruit to conspicuously increase its size and acquire its final shape and means for seed dispersal. All these features are key for plant survival and crop yield. Despite its importance, we lack a high-resolution spatiotemporal map of how postfertilization fruit growth proceeds at the cellular level. In this study, we have combined live imaging, mutant backgrounds in which fertilization can be controlled, and computational modeling to monitor and predict postfertilization fruit growth in Arabidopsis. We have uncovered that, unlike leaves, sepals, or roots, fruit do not exhibit a spatial separation of cell division and expansion domains; instead, there is a separation into temporal stages with fertilization as the trigger for transitioning to cell expansion, which drives postfertilization fruit growth. We quantified the coordination between fertilization and fruit growth by imaging no transmitting tract (ntt) mutants, in which fertilization fails in the bottom half of the fruit. By combining our experimental data with computational modeling, we delineated the mobility properties of the seed-derived signaling cascades promoting growth in the fruit. Our study provides the basis for generating a comprehensive understanding of the molecular and cellular mechanisms governing fruit growth and shape.

植物的果实演化出了一个精密组织以及细胞结构来保证植物生殖的成功。受精后生长可能是果实形态发生过程中变化最为剧烈的时刻。已有的一些研究认为受精的胚珠和发育中的种子起始了信号级联来协调并促进水果组织的生长。该动态过程使得水果能够明显地增加其大小，并且达到其最终种子传播时的形状和状态。这些特性对于植物的生存和作物的生产都是至关重要的。尽管该过程十分重要，我们仍缺少一个细胞层面上受精后果实生长的高分辨率时空图谱。本文中，作者结合了实时成像、受精可控的突变体株系以及计算建模来检测并预测拟南芥中的受精后果实生长。作者发现与叶片、萼片以及根不同是的，果实中并不存在一个细胞分裂和扩张的空间分隔；相反，却存在一个时间阶段分隔，受精诱导了果实组织进入到细胞扩张阶段，从而驱动了果实的受精后生长。作者利用一个果实下半部分受精失败的ntt突变体量化了受精与果实生长之间的协调性。结合本文的试验数据和计算建模，作者描绘了一个促进果实生长的、源自于种子的信号级联的流动性。本文的研究为全面理解作用于果实生长和形状的分子和细胞机制提供了基础。

通讯：Adrienne H. K. Roeder（https://roeder.wicmb.cornell.edu）

研究方向：拟南芥萼片中细胞生长和分裂在细胞大小多样性中的作用。

doi: https://doi.org/10.1073/pnas.1914096116

Journal: PNAS

First Published: November 22, 2019