Key message

The non-intrinsic ABC proteins ABCI20 and ABCI21 are induced by light under HY5 regulation, localize to the ER, and ameliorate cytokinin-driven growth inhibition in young Arabidopsis thaliana seedlings.

Abstract

The plant ATP-binding cassette (ABC) I subfamily (ABCIs) comprises heterogeneous proteins containing any of the domains found in other ABC proteins. Some ABCIs are known to function in basic metabolism and stress responses, but many remain functionally uncharacterized. ABCI19, ABCI20, and ABCI21 of Arabidopsis thaliana cluster together in a phylogenetic tree, and are suggested to be targets of the transcription factor ELONGATED HYPOCOTYL 5 (HY5). Here, we reveal that these three ABCIs are involved in modulating cytokinin responses during early seedling development. The ABCI19, ABCI20 and ABCI21 promoters harbor HY5-binding motifs, and ABCI20 and ABCI21 expression was induced by light in a HY5-dependent manner. abci19 abci20 abci21 triple and abci20 abci21 double knockout mutants were hypersensitive to cytokinin in seedling growth retardation assays, but did not show phenotypic differences from the wild type in either control medium or auxin-, ABA-, GA-, ACC- or BR-containing media. ABCI19, ABCI20, and ABCI21 were expressed in young seedlings and the three proteins interacted with each other, forming a large protein complex at the endoplasmic reticulum (ER) membrane. These results suggest that ABCI19, ABCI20, and ABCI21 fine-tune the cytokinin response at the ER under the control of HY5 at the young seedling stage.

中文翻译：

---

非内在 ATP 结合盒蛋白 ABCI19、ABCI20 和 ABCI21 调节拟南芥内质网的细胞分裂素反应。

关键信息

非内在 ABC 蛋白 ABCI20 和 ABCI21 在 HY5 调节下由光诱导，定位于 ER，并改善拟南芥幼苗中细胞分裂素驱动的生长抑制。

抽象的

植物 ATP 结合盒 (ABC) I 亚家族 (ABCIs) 包含异质蛋白，其中包含在其他 ABC 蛋白中发现的任何结构域。一些 ABCI 已知在基本代谢和应激反应中起作用，但许多仍然在功能上没有特征。拟南芥的 ABCI19、ABCI20 和 ABCI21在系统发育树中聚集在一起，被认为是转录因子 ELONGATED HYPOCOTYL 5 (HY5) 的靶标。在这里，我们揭示了这三种 ABCI 在早期幼苗发育过程中参与调节细胞分裂素反应。ABCI19 、ABCI20和ABCI21启动子含有HY5 结合基序，而ABCI20和ABCI21表达是由光以 HY5 依赖性方式诱导的。abci19 abci20 abci21三重和abci20 abci21双敲除突变体在幼苗生长迟缓试验中对细胞分裂素过敏，但在对照培养基或含有生长素、ABA-、GA-或 BR 的培养基中均未显示出与野生型的表型差异媒体。ABCI19、ABCI20和ABCI21在幼苗中表达，三种蛋白质相互作用，在内质网(ER)膜上形成一个大的蛋白质复合物。这些结果表明 ABCI19、ABCI20 和 ABCI21 在幼苗期在 HY5 的控制下微调 ER 的细胞分裂素反应。