属间杂交是种质资源创新的重要途径之一，项目组吴江生教授通过萝卜和甘蓝杂交、染色体加倍技术，结合连续多年的田间和实验室选择获得了遗传稳定的属间异源四倍体新种质Raphanobrassica（萝卜甘蓝）。前期研究表明，Raphanobrassica具有优良的抗根肿病和抗菌核病特性，在油菜抗病育种中具有很好的应用前景。

Raphanobrassica的角果出现了非常有趣的表型，表型观察发现萝卜甘蓝的角果上部不含有隔膜，而且果喙部较长较尖，这与母本萝卜的角果性状相似；然而角果的下部含有隔膜，而且种子粒数比上部的多，这与父本甘蓝的角果性状比较相似。总体来看，萝卜甘蓝的角果的长度，宽度，每角果种子粒数，种子大小，千粒重及颜色均位于两本的之间，但明显的更偏向于父本甘蓝。

Generation of Raphanobrassica, comparison of phenotypes among the hybrid and its diploid progenitors and synteny analysis between R^sR^s and C^oC^o genomes. (a) Schematic diagram for the generation of allotetraploid Raphanobrassica. (b) Comparisons of the whole silique, pod and seed phenotypes among the hybrid and its diploid parents at 35 DAF. The black arrow indicates a sponge-like membrane enclosing R^sR^s seeds. Scale bars, 1 cm. (c) Magnified images of those from (b) in white rectangular boxes. Arrows indicate the dehiscence zones of Csi and RCsil. (d) Silique length (without the tip) of R^sR^s, C^oC^o, R^rR^rC^rC^r, upper and lower parts of the R^rR^rC^rC^r silique at 35 DAF. Error bars, standard deviation. (e) Number of seeds per silique of R^sR^s, C^oC^o, R^rR^rC^rC^r, upper and lower parts of R^rR^rC^rC^r silique.

近日，本课题组在Horticulture Research发表了标题为 “Genome-wide unbalanced expression bias and expression level dominance toward Brassica oleracea in artificially synthesized intergeneric hybrids of Raphanobrassica”的研究论文 (论文链接：https://www.nature.com/articles/s41438-021-00672-2)。该研究论文对对人工杂合体萝卜甘蓝角果的不同部位及其亲本的角果进行基因表达模式的综合分析。随后对花后35天的属间杂种Raphanobrassica、杂交亲本萝卜和甘蓝的角果皮和种子中的基因表达模式进行了分析，发现Raphanobrassica角果皮的上部、中部、下部及种子中40%左右基因的表达水平呈现为甘蓝显性（Expression level dominance），这与该杂合体角果表现出的性状非常吻合。

Expression level dominance and relationships between the ELD and individual homoeolog expression levels. (a) ELD in the three sections of pods and RCseu of Raphanobrassica, reflecting the collective expression of homoeolog pairs compared to those in the progenitors. (b) Relationships between ELD and individual homoeolog expression levels explained the phenomenon of ELD in the four tissues.

Homoeolog expression bias总体上也明显偏向于甘蓝，但不同部位的偏向性有所差别。和亲本材料相比，Raphanobrassica角果中大量基因发生了明显转录组休克（Transcriptome shock）现象，其表达水平都出现了明显下调。本文相关研究为异缘多倍体中的基因表达分析提供了新思路。

Analysis of homoeolog expression bias of homoeologous gene pairs in R^rR^rC^rC^r. (a) Homoeolog expression bias analyses of RCsiu, (b) RCsim, (c) RCsil and (d) RCseu. The numbers of homoeolog pairs and their proportions to the total numbers of analyzed pairs are listed. The sizes of the circles in the diploid progenitor R^sR^s and C^oC^o indicated the relative expression levels of the orthologs (homoeologs in the hybrid), while relative expression levels of the homoeologs in R^rR^rC^rC^r were indicated by the area ratio of the circles. In addition, the numbers in red indicate that the expression patterns of homoeologs in R^rR^rC^rC^r maintained parental conditions, while those in blue indicate novel expression bias in the hybrid.