生长素和赤霉素调控草莓果实大小和形状的功能和分子机理研究

Fruits shape is one of common interest in horticultural science. The variation of fruits shape and size often attracts consumers. Strawberry (Fragaria × ananassa Duch.) is one of model plant in rosacea families. Plant hormones, auxin and gibberellin (GA), play important role in strawberry fruits development. Previous studies showed the evidence that auxin function in fruits development is partially dependent on GA function. Furthermore, our results showed that Auxin mainly regulates breadth of receptacle fruits, in while GA promotes length of receptacle fruits, thus coordinate receptacle fruits shape and size. However, the molecular mechanism of auxin and GA function in fruits development and that how these plant hormones coordinate their specific role in fruit development is largely unknown in strawberry. To understand how the actions of auxin and GA are coordinated to control strawberry fruit development, and to use this knowledge for the manipulation of fruits size and shape in fruit production, we use woodland diploid strawberry, Fragaria vesca as an exciting model system. Toward our goal, we will establish gene expression profile of fruits development by using fertilization dependent and independent strawberry fruits (caused by auxin or GA treatment) as a model system, and figure out the next breeding target. The analysis of fruits size and shape controller candidates with genetic evidence is also included in this proposal. Our results will perform detailed analysis with focus on auxin and GA function and establish the model system of plant hormone interactions network in fruits development. Our proposed works has potential to contribute to not only breeding science but also for basic science.

果实的形状和大小是吸引消费者的重要因素，因此，果形的调控机理是果树学科的研究热点之一。草莓(Fragaria × ananassa Duch.) 属于蔷薇科,是研究果实发育的模式植物之一。以往的研究表明，生长素（Auxin）和赤霉素（GA）促进草莓果实发育，且Auxin在果实发育中的作用部分依赖于GA。我们的研究结果表明，Auxin和GA分别主要促进果实横径和纵径的生长，从而协同调控果实的形状和大小。然而，目前对于Auxin和GA调控果实形状和大小的分子机理却不清楚。为此，本研究以森林草莓‘Yellow Wonder’为试材，利用正常授粉和NAA或GA3处理的草莓果实作为模型系统，建立果实发育的基因表达谱，解析对果实大小和形状的潜在调控因子的功能。本项目将在细胞水平和分子水平对Auxin和GA在果实发育中的功能进行详细的分析，进一步建立植物激素相互作用网络在果实发育调控中的模型体系。

果实的形状和大小是吸引消费者的重要因素，因此，果形的调控机理一直是园艺学科的研究热点之一。我们先前的研究结果表明，auxin和GA分别主要促进草莓果实横径和纵径的生长，从而协同调控果实的形状和大小，但潜在的分子机制仍不清楚。本项目利用外源NAA、GA3和NG(NAA+GA3)处理未授粉的二倍体森林草莓“Yellow Wonder”果实，通过制作石蜡切片，研究了这两种激素对果实不同组织中细胞发育和分化的影响。其中Auxin主要促进Cortex和Pith1中细胞的膨大，而GA主要促进Pith1细胞的伸长，Pith2中细胞的分化。并进一步通过转录组分析，鉴定了果实不同组织中响应四种信号路径的基因：①auxin特异响应路径；②GA特异响路径；③auxin和GA交叉路径；④auxin和GA协同调控路径。每条路径中对应的转录因子也已鉴定。其中， GA独立路径中的多个转录因子与DELLA蛋白互作，例如TCP14转录因子。此外，本项目还利用WGCNA分析，构建共表达网络。这些不同信号路径基因的鉴定以及共表达网络的构建，将有助于进一步解析auxin和GA调控草莓果实发育分子机理。