Harel-Beja Rotem, Ophir Ron, Sherman Amir, Eshed Ravit, Rozen Ada, Trainin Taly, Doron-Faigenboim Adi, Tal Ofir, Bar-Yaakov Irit, Holland Doron
Department of Fruit Tree Sciences, Institute of Plant Sciences, Agricultural Research Organization - The Volcani Center, Newe Ya'ar Research Center, Ramat Yishai, Israel.
Department of Fruit Tree Sciences, Institute of Plant Sciences, Agricultural Research Organization - The Volcani Center, Rishon LeZion, Israel.
Front Plant Sci. 2022 Apr 29;13:870207. doi: 10.3389/fpls.2022.870207. eCollection 2022.
The pomegranate ( L.) is a deciduous fruit tree that grows worldwide. However, there are variants, which stay green in mild winter conditions and are determined evergreen. The evergreen trait is of commercial and scientific importance as it extends the period of fruit production and provides opportunity to identify genetic functions that are involved in sensing environmental cues. Several different evergreen pomegranate accessions from different genetic sources grow in the Israeli pomegranate collection. The leaves of deciduous pomegranates begin to lose chlorophyll during mid of September, while evergreen accessions continue to generate new buds. When winter temperature decreases 10°C, evergreen variants cease growing, but as soon as temperatures arise budding starts, weeks before the response of the deciduous varieties. In order to understand the genetic components that control the evergreen/deciduous phenotype, several segregating populations were constructed, and high-resolution genetic maps were assembled. Analysis of three segregating populations showed that the evergreen/deciduous trait in pomegranate is controlled by one major gene that mapped to linkage group 3. Fine mapping with advanced F3 and F4 populations and data from the pomegranate genome sequences revealed that a gene encoding for a putative and unique MADS transcription factor () is responsible for the evergreen trait. Ectopic expression of in Arabidopsis generated small plants and early flowering. The deduced protein of includes eight glutamines (polyQ) at the N-terminus. Three-dimensional protein model suggests that the polyQ domain structure might be involved in DNA binding of PgMADS. Interestingly, all the evergreen pomegranate varieties contain a mutation within the polyQ that cause a stop codon at the N terminal. The polyQ domain of PgPolyQ-MADS resembles that of the ELF3 prion-like domain recently reported to act as a thermo-sensor in Arabidopsis, suggesting that similar function could be attributed to PgPolyQ-MADS protein in control of dormancy. The study of the evergreen trait broadens our understanding of the molecular mechanism related to response to environmental cues. This enables the development of new cultivars that are better adapted to a wide range of climatic conditions.
石榴（L.）是一种在全球范围内生长的落叶果树。然而，存在一些变种，它们在温和的冬季条件下保持绿色，被确定为常绿品种。常绿特性具有商业和科学重要性，因为它延长了果实生产期，并为鉴定参与感知环境线索的基因功能提供了机会。来自不同遗传来源的几种不同的常绿石榴种质在以色列石榴种质库中生长。落叶石榴的叶子在9月中旬开始失去叶绿素，而常绿种质则继续产生新芽。当冬季温度降至10°C时，常绿变种停止生长，但一旦温度升高，发芽就开始，比落叶品种的反应提前几周。为了了解控制常绿/落叶表型的遗传成分，构建了几个分离群体，并组装了高分辨率遗传图谱。对三个分离群体的分析表明，石榴的常绿/落叶性状由一个主要基因控制，该基因定位于连锁群3。利用先进的F3和F4群体进行精细定位以及来自石榴基因组序列的数据表明，一个编码假定的独特MADS转录因子（）的基因负责常绿性状。在拟南芥中异位表达该基因产生了矮小植株和早花现象。该基因推导的蛋白质在N端包含八个谷氨酰胺（polyQ）。三维蛋白质模型表明，polyQ结构域可能参与了PgMADS与DNA的结合。有趣的是，所有常绿石榴品种在polyQ内都含有一个突变，该突变在N端导致了一个终止密码子。PgPolyQ-MADS的polyQ结构域类似于最近报道在拟南芥中作为热传感器起作用的ELF3朊病毒样结构域，这表明PgPolyQ-MADS蛋白在控制休眠方面可能具有类似功能。对常绿性状的研究拓宽了我们对与环境线索响应相关分子机制的理解。这有助于开发更能适应广泛气候条件的新品种。
