a Department of Horticulture, Zijingang Campus , Zhejiang University , Hangzhou , China.
b Department of Botany and Plant Pathology and Purdue Center for Plant Biology , Purdue University , West Lafayette , IN , USA.
Autophagy. 2018;14(3):487-504. doi: 10.1080/15548627.2017.1422856. Epub 2018 Feb 21.
Selective macroautophagy/autophagy targets specific cargo by autophagy receptors through interaction with ATG8 (autophagy-related protein 8)/MAP1LC3 (microtubule associated protein 1 light chain 3) for degradation in the vacuole. Here, we report the identification and characterization of 3 related ATG8-interacting proteins (AT1G17780/ATI3A, AT2G16575/ATI3B and AT1G73130/ATI3C) from Arabidopsis. ATI3 proteins contain a WxxL LC3-interacting region (LIR) motif at the C terminus required for interaction with ATG8. ATI3 homologs are found only in dicots but not in other organisms including monocots. Disruption of ATI3A does not alter plant growth or development but compromises both plant heat tolerance and resistance to the necrotrophic fungal pathogen Botrytis cinerea. The critical role of ATI3A in plant stress tolerance and disease resistance is dependent on its interaction with ATG8. Disruption of ATI3B and ATI3C also significantly compromises plant heat tolerance. ATI3A interacts with AT3G56740/UBAC2A and AT2G41160/UBAC2B (Ubiquitin-associated [UBA] protein 2a/b), 2 conserved proteins implicated in endoplasmic reticulum (ER)-associated degradation. Disruption of UBAC2A and UBAC2B also compromised heat tolerance and resistance to B. cinerea. Overexpression of UBAC2 induces formation of ATG8- and ATI3-labeled punctate structures under normal conditions, likely reflecting increased formation of phagophores or autophagosomes. The ati3 and ubac2 mutants are significantly compromised in sensitivity to tunicamycin, an ER stress-inducing agent, but are fully competent in autophagy-dependent ER degradation under conditions of ER stress when using an ER lumenal marker for detection. We propose that ATI3 and UBAC2 play an important role in plant stress responses by mediating selective autophagy of specific unknown ER components.
选择性的巨自噬/自噬通过自噬受体与 ATG8（自噬相关蛋白 8）/MAP1LC3（微管相关蛋白 1 轻链 3）相互作用，对溶酶体中的特定货物进行降解。在这里，我们从拟南芥中鉴定并描述了 3 种相关的 ATG8 相互作用蛋白（AT1G17780/ATI3A、AT2G16575/ATI3B 和 AT1G73130/ATI3C）。ATI3 蛋白在 C 端含有一个 WxxL LC3 相互作用区域（LIR）基序，该基序对于与 ATG8 的相互作用是必需的。ATI3 同源物仅存在于双子叶植物中，而不存在于其他生物中，包括单子叶植物。ATI3A 的缺失不会改变植物的生长或发育，但会损害植物对热的耐受性和对坏死真菌病原体 Botrytis cinerea 的抗性。ATI3A 在植物应激耐受和疾病抗性中的关键作用依赖于其与 ATG8 的相互作用。ATI3B 和 ATI3C 的缺失也显著损害了植物对热的耐受性。ATI3A 与 AT3G56740/UBAC2A 和 AT2G41160/UBAC2B（泛素相关[UBA]蛋白 2a/b）相互作用，UBAC2A 和 UBAC2B 是两种与内质网（ER）相关降解有关的保守蛋白。UBAC2A 和 UBAC2B 的缺失也损害了植物对热的耐受性和对 Botrytis cinerea 的抗性。UBAC2 的过表达在正常条件下诱导形成 ATG8 和 ATI3 标记的点状结构，这可能反映了吞噬体或自噬体形成的增加。在 tunicamycin（一种诱导内质网应激的试剂）的敏感性方面，ati3 和 ubac2 突变体显著受损，但在使用 ER 腔标记物进行检测时，在 ER 应激条件下，自噬依赖性 ER 降解完全有效。我们提出，ATI3 和 UBAC2 通过介导特定未知 ER 成分的选择性自噬，在植物应激反应中发挥重要作用。
