Os01g0703600

SPL28 encodes a clathrin-associated adaptor protein complex 1, medium subunit μ1 (AP1M1) and is responsible for spotted leaf and early senescence in rice.

Annotated Information

Gene Symbol

• Os01g0703600 <=> SPL28

Function

Fig 1. Phenotype of the spotted leaf 28 (spl28) mutant .

Fig 6. Map-based cloning and identification of SPOTTED LEAF 28 (SPL28) .

A novel rice (Oryza sativa) spotted leaf mutant (spl28) that displays a lesion mimic phenotype in the absence of pathogen attack was isolated through treatment of Hwacheongbyeo (an elite Korean japonica cultivar) with N-methyl-N-nitrosourea (MNU). Early stage development of the spl28 mutant was normal. However, after flowering, spl28 mutants exhibited a significant decrease in chlorophyll content, soluble protein content, and photosystem II efficiency, and high concentrations of reactive oxygen species (ROS), phytoalexin, callose, and autofluorescent phenolic compounds that localized in or around the lesions. The spl28 mutant also exhibited significantly enhanced resistance to rice blast and bacterial blight. Using a map-based cloning approach, SPL28 was determined to encode a clathrin-associated adaptor protein complex 1, medium subunit μ1 (AP1M1), which is involved in the post-Golgi trafficking pathway. A green fluorescent protein (GFP) fusion protein of SPL28 (SPL28::GFP) localized to the Golgi apparatus, and expression of SPL28 complemented the membrane trafficking defect of apm1-1Δ yeast mutants. SPL28 was ubiquitously expressed and contained a highly conserved adaptor complex medium subunit (ACMS) family domain. SPL28 appears to be involved in the regulation of vesicular trafficking, and SPL28 dysfunction causes the formation of hypersensitive response (HR)-like lesions, leading to the initiation of leaf senescence .

Expression

Fig 9. Subcellular localization of SPOTTED LEAF 28 (SPL28)-green fluorescent protein (GFP) fusion protein in onion epidermal cells .

SPL28 was expressed in all organs examined. In wild-type plants, SPL28 mRNA was most abundant in the root, leaf and panicle, and was weakly detected in the stem, which indicated that SPL28 is expressed in a tissue-specific manner. SPL28 transcripts exhibited the opposite trend in spl28 mutant plants. The spl28 phenotype was reminiscent of mutants in which defense signaling pathways are constitutively active. The expression of two defense signaling-related genes, PR1 and PR2, was also examined in wild-type and spl28 mutant plants. Based on RT-PCR analysis, PR1 and PR2 in the spl28 mutant were strongly expressed. In addition, SAG12, a gene that encodes a cysteine protease that accumulates during leaf senescence, was strongly expressed in spl28 mutants.

The subcellular localization of SPL28 was in the Golgi apparatus (Fig. 9), which indicated that SPL28 might be involved in the regulation of clathrin-associated adaptor prtein complex 1 (AP-1) membrane-cytoplasm recycling, together with clathrin, during transport vesicle formation and vesicle uncoating in rice.

Evolution

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Labs working on this gene

• Department of Plant Science, Research Institute for Agriculture and Life Sciences, and Plant Genomics and Breeding Institute, Seoul National University, Seoul, 151-921, Republic of Korea;
• Crop Environment and Biotechnology Division, National Institute of Crop Science, RDA, Suwon, 441-857, Republic of Korea;
• Key Laboratory of Crop Germplasm Resources and Biotechnology, Ministry of Agriculture, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China