Brassicaceae and closely related species develop unique endoplasmic reticulum (ER)-derived structures called ER bodies, which accumulate β-glucosidases/myrosinases that are involved in chemical defense. There are two different types of ER bodies: ER bodies constitutively present in seedlings (cER bodies) and ER bodies in rosette leaves induced by treatment with the wounding hormone jasmonate (JA) (iER bodies). Here, we show that At-α whole-genome duplication (WGD) generated the paralogous genes NAI2 and TSA1, which consequently drive differentiation of cER bodies and iER bodies in Brassicaceae plants. In Arabidopsis, NAI2 is expressed in seedlings where cER bodies are formed, whereas TSA1 is expressed in JA-treated leaves where iER bodies are formed. We found that the expression of NAI2 in seedlings and the JA inducibility of TSA1 are conserved across other Brassicaceae plants. The accumulation of NAI2 transcripts in Arabidopsis seedlings is dependent on the transcription factor NAI1, whereas the JA induction of TSA1 in rosette leaves is dependent on MYC2, MYC3 and MYC4. We discovered regions of microsynteny, including the NAI2/TSA1 genes, but the promoter regions are differentiated between TSA1 and NAI2 genes in Brassicaceae. This suggests that the divergence of function between NAI2 and TSA1 occurred immediately after WGD in ancestral Brassicaceae plants to differentiate the formation of iER and cER bodies. Our findings indicate that At-α WGD enabled diversification of defense strategies, which may have contributed to the massive diversification of Brassicaceae plants.

中文翻译：

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NAI2和TSA1推动了十字花科植物本构和诱导型ER体形成的分化。

十字花科和密切相关的物种会发育出独特的内质网（ER）衍生结构，称为ER体，这些结构会积聚参与化学防御作用的β-葡萄糖苷酶/黑芥子酶。有两种不同类型的ER体：组成型存在于幼苗中的ER体（cER体）和玫瑰花叶中的ER体（通过创伤性茉莉酮酸（JA）的处理诱导）（iER体）。在这里，我们显示At-α全基因组复制（WGD）产生了旁系同源基因NAI2和TSA1，从而推动了十字花科植物中cER体和iER体的分化。在拟南芥中，NAI2在形成cER体的幼苗中表达，而TSA1在形成iER体的经JA处理的叶片中表达。我们发现，在其他十字花科植物中，NAI2在幼苗中的表达和TSA1的JA诱导性是保守的。拟南芥幼苗中NAI2转录物的积累取决于转录因子NAI1，而莲座叶中TSA1的JA诱导则取决于MYC2，MYC3和MYC4。我们发现了微同域，包括NAI2 / TSA1基因，但启动子区域在十字花科的TSA1和NAI2基因之间有所区别。这表明在祖先十字花科植物中WGD后，NAI2和TSA1之间的功能发生了分化，从而区分了iER和cER体的形成。我们的发现表明，At-αWGD能够实现防御策略的多样化，这可能有助于十字花科植物的大规模多样化。