Language：Japanese  

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Language：English   Publisher：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

Serotonin is a well known neurotransmitter in mammals and plays an important role in various mental functions in humans. In plants, the serotonin biosynthesis pathway and its function are not well understood. The rice sekiguchi lesion (sl) mutants accumulate tryptamine, a candidate substrate for serotonin biosynthesis. We isolated the SL gene by map-based cloning and found that it encodes CYP71P1 in a cytochrome P450 monooxygenase family. A recombinant SL protein exhibited tryptamine 5-hydroxylase enzyme activity and catalyzed the conversion of tryptamine to serotonin. This pathway is novel and has not been reported in mammals. Expression of SL was induced by the N-acetylchitooligosaccharide (chitin) elicitor and by infection with Magnaporthe grisea, a causal agent for rice blast disease. Exogenously applied serotonin induced defense gene expression and cell death in rice suspension cultures and increased resistance to rice blast infection in plants. We also found that serotonin-induced defense gene expression is mediated by the RacGTPase pathway and by the G alpha subunit of the heterotrimeric G protein. These results suggest that serotonin plays an important role in rice innate immunity.

DOI： 10.1074/jbc.M109.091371

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Language：English   Publisher：JAPANESE SOC PLANT CELL & MOLECULAR BIOL  

Five non-allelic dull (du) mutants have been isolated and characterized as low amylose mutants in rice (Oryza sativa) endosperm. Synthesis of amylose is controlled by Waxy the gene that encodes granule-bound starch synthase. We previously showed that the du1 and du2 proteins may encode general splicing regulators which affect the expression level and splicing efficiency of Waxy(b) (Wx(b)), an allele that has a single-base mutation in the 5' splice site of intron 1. Here we report that the du3 mutant has also reduced the splicing efficiency of Wx(b) pre-mRNA. Furthermore, map-based cloning revealed that Du3 encodes the rice homolog of a cap-binding protein 20 kD subunit (CBP20), a component of the heterodimeric nuclear cap-binding complex (CBC) playing a role in pre-mRNA splicing, RNA nuclear export, and nonsense-mediated decay. Transient expression of green fluorescent protein (GFP)-tagged Du3 proteins in rice protoplasts resulted in localization to the nucleus showing a speckled pattern similar to the pattern displayed by other splicing factors.

DOI： 10.5511/plantbiotechnology.25.483

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Language：English   Publisher：AMER SOC PLANT BIOLOGISTS  

Ser/Arg-rich (SR) proteins play important roles in the constitutive and alternative splicing of pre-mRNA. We isolated 20 rice (Oryza sativa) genes encoding SR proteins, of which six contain plant-specific characteristics. To determine whether SR proteins modulate splicing efficiency and alternative splicing of pre-mRNA in rice, we used transient assays in rice protoplasts by cotransformation of SR protein genes with the rice Waxy(b) (Wx(b))-beta-glucuronidase fusion gene. The results showed that plant-specific RSp29 and RSZp23, an SR protein homologous to human 9G8, enhanced splicing and altered the alternative 5' splice sites of Wx(b) intron 1. The resulting splicing pattern was unique to each SR protein; RSp29 stimulated splicing at the distal site, and RSZp23 enhanced splicing at the proximal site. Results of domain-swapping experiments between plant-specific RSp29 and SCL26, which is a homolog of human SC35, showed the importance of RNA recognition motif 1 and the Arg/Ser-rich (RS) domain for the enhancement of splicing efficiencies. Overexpression of plant-specific RSZ36 and SRp33b, a homolog of human ASF/SF2, in transgenic rice changed the alternative splicing patterns of their own pre-mRNAs and those of other SR proteins. These results show that SR proteins play important roles in constitutive and alternative splicing of rice pre-mRNA.

DOI： 10.1105/tpc.105.037069

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Presentation type：Poster presentation  

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