Li Ruixi, Sun Ruobai, Hicks Glenn R, Raikhel Natasha V
Department of Botany and Plant Sciences, Center for Plant Cell Biology, Institute for Integrative Genome Biology, University of California, Riverside, CA 92521.
Department of Botany and Plant Sciences, Center for Plant Cell Biology, Institute for Integrative Genome Biology, University of California, Riverside, CA 92521
Proc Natl Acad Sci U S A. 2015 Jan 6;112(1):E89-98. doi: 10.1073/pnas.1422656112. Epub 2014 Dec 22.
The vacuole is the most prominent compartment in plant cells and is important for ion and protein storage. In our effort to search for key regulators in the plant vacuole sorting pathway, ribosomal large subunit 4 (rpl4d) was identified as a translational mutant defective in both vacuole trafficking and normal development. Polysome profiling of the rpl4d mutant showed reduction in polysome-bound mRNA compared with wild-type, but no significant change in the general mRNA distribution pattern. Ribsomal profiling data indicated that genes in the lipid metabolism pathways were translationally down-regulated in the rpl4d mutant. Live imaging studies by Nile red staining suggested that both polar and nonpolar lipid accumulation was reduced in meristem tissues of rpl4d mutants. Pharmacological evidence showed that sterol and sphingolipid biosynthetic inhibitors can phenocopy the defects of the rpl4d mutant, including an altered vacuole trafficking pattern. Genetic evidence from lipid biosynthetic mutants indicates that alteration in the metabolism of either sterol or sphingolipid biosynthesis resulted in vacuole trafficking defects, similar to the rpl4d mutant. Tissue-specific complementation with key enzymes from lipid biosynthesis pathways can partially rescue both vacuole trafficking and auxin-related developmental defects in the rpl4d mutant. These results indicate that lipid metabolism modulates auxin-mediated tissue differentiation and endomembrane trafficking pathways downstream of ribosomal protein function.
液泡是植物细胞中最显著的区室，对离子和蛋白质的储存很重要。在我们寻找植物液泡分选途径关键调节因子的过程中，核糖体大亚基4（rpl4d）被鉴定为一个在液泡运输和正常发育方面均有缺陷的翻译突变体。rpl4d突变体的多核糖体分析显示，与野生型相比，结合多核糖体的mRNA减少，但总体mRNA分布模式没有显著变化。核糖体分析数据表明，脂质代谢途径中的基因在rpl4d突变体中翻译水平下调。尼罗红染色的活细胞成像研究表明，rpl4d突变体分生组织中的极性和非极性脂质积累均减少。药理学证据表明，固醇和鞘脂生物合成抑制剂可模拟rpl4d突变体的缺陷，包括改变液泡运输模式。来自脂质生物合成突变体的遗传学证据表明，固醇或鞘脂生物合成代谢的改变会导致液泡运输缺陷，类似于rpl4d突变体。用脂质生物合成途径的关键酶进行组织特异性互补可部分挽救rpl4d突变体中的液泡运输和生长素相关的发育缺陷。这些结果表明，脂质代谢调节生长素介导的组织分化以及核糖体蛋白功能下游的内膜运输途径。
