The rice α-amylase glycoprotein is targeted from the golgi apparatus through the secretory pathway to the plastids

Aya Kitajima, Satoru Asatsuma, Hisao Okada, Yuki Hamada, Kentaro Kaneko, Yohei Nanjo, Yasushi Kawagoe, Kiminori Toyooka, Ken Matsuoka, Masaki Takeuchi, Akihiko Nakano, Toshiaki Mitsui

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107 Citations (Scopus)


The well-characterized secretory glycoprotein, rice [Oryza sativa) α-amylase isoform I-1 (Amyl-1), was localized within the plastids and proved to be involved in the degradation of starch granules in the organelles of rice cells. In addition, a large portion of transiently expressed Amyl-1 fused to green fluorescent protein (Amyl-1-GFP) colocalized with a simultaneously expressed fluorescent plastid marker in onion (Allium cepa) epidermal cells. The plastid targeting of Amyl-1 was inhibited by both dominant-negative and constitutively active mutants of Arabidopsis thaliana ARF1 and Arabidopsis SAR1, which arrest endoplasmic reticulum-to-Golgi traffic. In cells expressing fluorescent frans-Golgi and plastid markers, these fluorescent markers frequently colocalized when coexpressed with Amyl-1. Three-dimensional time-lapse imaging and electron microscopy of high-pressure frozen/freeze- substituted cells demonstrated that contact of the Golgi-derived membrane vesicles with cargo and subsequent absorption into plastids occur within the cells. The transient expression of a series of C-terminal-truncated Amyl-1-GFP fusion proteins in the onion cell system showed that the region from Trp-301 to Gln-369 is necessary for plastid targeting of Amyl-1. Furthermore, the results obtained by site-directed mutations of Trp-302 and Gly354, located on the surface and on opposite sides of the Amyl-1 protein, suggest that multiple surface regions are necessary for plastid targeting. Thus, Golgi-to-plastid traffic appears to be involved in the transport of glycoproteins to plastids and plastid targeting seems to be accomplished in a sorting signal-dependent manner.

Original languageEnglish
Pages (from-to)2844-2858
Number of pages15
JournalPlant Cell
Issue number9
Publication statusPublished - 2009

All Science Journal Classification (ASJC) codes

  • Plant Science
  • Cell Biology


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