Abstract
NMD3 is required for nuclear export of the 60S ribosomal subunit in yeast and vertebrate cells, but no corresponding function of NMD3 has been reported in plants. Here we report that Arabidopsis thaliana NMD3 (AtNMD3) showed a similar function in the nuclear export of the 60S ribosomal subunit. Interference with AtNMD3 function by overexpressing a truncated dominant negative form of the protein lacking the nuclear export signal sequence caused retainment of the 60S ribosomal subunits in the nuclei. More interestingly, the transgenic Arabidopsis with dominant negative interference of AtNMD3 function showed a striking failure of secondary cell wall thickening, consistent with the altered expression of related genes and composition of cell wall components. Observation of a significant decrease of rough endoplasmic reticulum (RER) in the differentiating interfascicular fiber cells of the transgenic plant stems suggested a link between the defective nuclear export of 60S ribosomal subunits and the abnormal formation of the secondary cell wall. These findings not only clarified the evolutionary conservation of NMD3 functions in the nuclear export of 60S ribosomal subunits in yeast, animals and plants, but also revealed a new facet of the regulatory mechanism underlying secondary cell wall thickening in Arabidopsis. This new facet is that the nuclear export of 60S ribosomal subunits and the formation of RER may play regulatory roles in coordinating protein synthesis in cytoplasm and transcription in nuclei.
Highlights
Ribosomes have been long known as the main components of the protein synthesis machinery in cells
Phylogenetic Analysis of Arabidopsis thaliana NMD3 (AtNMD3) To systematically analyze the function of AtNMD3, we carried out a phylogenetic analysis using the neighbor-joining method with 36 representative species, including 28 photosynthetic organisms (Figure 1)
We demonstrated that the Arabidopsis AtNMD3 protein has a similar function
Summary
Ribosomes have been long known as the main components of the protein synthesis machinery in cells. Mutations in ribosomal protein genes affecting aspects of development such as embryogenesis (RPS11A, RPL3A, RPL8A, RPL19A, RPL23C, and RPL40B) [6] and leaf shape Five genes related to ribosome biogenesis (OLIGOCELLUA2, AtNUC-L1, EBP1, TORMOZ and SLOW WALKER1) have been reported to be involved in plant development in different ways [18]. These findings have only begun to reveal the potential mechanisms of ribosomemediated regulatory functions
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