The fruit-weight 2.2 (fw2.2) locus, which was first described in tomato, is known for controlling up to 30% of fruit mass. The functions of its homologs, the FW2.2-like (FWL) genes, have also been documented in other diploid plants such as maize and rice. However, the evolution and contribution of the FWL gene family to seed weight in polyploid crops remain to be explored. In this study, we deployed an integrated approach to characterize the FWL gene family in the allotetraploid crop, Brassica napus. A total of 18 FWL genes were identified and designated BnFWL1–18. These were classified into three groups based on their phylogenetic relationships, which were supported by multiple sequence alignment, chromosome location, collinearity, transmembrane prediction, conserved motifs, selection pressure, protein three-dimensional (3D) structure, and the composition and position of cis-regulatory elements. Strikingly, three conserved 3D models were identified in all 18 BnFWL proteins, pertaining to the soluble N-ethylmaleimide-sensitive factor attachment protein receptor complex. Intriguingly, we found that the BnFWL12 protein was structurally similar to phosphoenolpyruvate carboxylase, which is required for photosynthesis. More importantly, we identified an “SDGE” phosphorylation motif in BnFWL12 in a search for putative casein kinase II (CK2) phosphorylation sites. Moreover, the temporospatial expression profiles in different tissues revealed that the discrete expression patterns are likely associated with the functional differentiation of BnFWL genes. Taken together, our data shed light on the evolutionary divergence of the FWL gene family in a polyploid crop, providing foundations for further functional studies.

中文翻译：

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多倍体油菜（Brassica napus L.）的果重2.2样基因家族的全基因组鉴定和进化分析。

最初在番茄中描述的果实重量2.2（fw2.2）位点可控制多达30％的果实质量。其同系物的功能，如FW2.2-like （FWL）基因，也已在其他二倍体植物如玉米和水稻中得到记录。然而，FWL基因家族的进化和对多倍体作物种子重量的贡献尚待探索。在这项研究中，我们部署了一种集成方法来表征异源四倍体作物甘蓝型油菜的FWL基因家族。总共鉴定出18个FWL基因并将其命名为BnFWL1-18。根据它们的系统发生关系，将它们分为三类，分别由多序列比对，染色体位置，共线性，跨膜预测，保守基序，选择压力，蛋白质三维（3D）结构以及顺式的组成和位置支持-调节元素。令人惊讶的是，在所有18种BnFWL蛋白中鉴定了三个保守的3D模型，涉及可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体复合物。有趣的是，我们发现BnFWL12蛋白在结构上与光合作用所需的磷酸烯醇丙酮酸羧化酶相似。更重要的是，在寻找假定的酪蛋白激酶II（CK2）磷酸化位点的过程中，我们在BnFWL12中鉴定了一个“ SDGE”磷酸化基序。此外，在不同组织中的颞expression表达谱显示，离散表达模式可能与BnFWL基因的功能分化有关。综上所述，我们的数据揭示了多倍体作物中FWL基因家族的进化差异，为进一步的功能研究奠定了基础。