Suppression of the rice fatty-acid desaturase gene OsSSI2 enhances resistance to blast and leaf blight diseases in rice.
Fatty acids and their derivatives play important signaling roles in plant defense responses. It has been shown that suppressing a gene for stearoyl acyl carrier protein fatty-acid desaturase (SACPD) enhances the resistance of Arabidopsis (SSI2) and soybean to multiple pathogens. In this study, we present functional analyses of a rice homolog of SSI2 (OsSSI2) in disease resistance of rice plants. A transposon insertion mutation (Osssi2-Tos17) and RNAi-mediated knockdown of OsSSI2 (OsSSI2-kd) reduced the oleic acid (18:1) level and increased that of stearic acid (18:0), indicating that OsSSI2 is responsible for fatty-acid desaturase activity. These plants displayed spontaneous lesion formation in leaf blades, retarded growth, slight increase in endogenous free salicylic acid (SA) levels, and SA/benzothiadiazole (BTH)-specific inducible genes, including WRKY45, a key regulator of SA/BTH-induced resistance, in rice. Moreover, the OsSSI2-kd plants showed markedly enhanced resistance to the blast fungus Magnaporthe grisea and leaf-blight bacteria Xanthomonas oryzae pv. oryzae. These results suggest that OsSSI2 is involved in the negative regulation of defense responses in rice, as are its Arabidopsis and soybean counterparts. Microarray analyses identified 406 genes that were differentially expressed (>or=2-fold) in OsSSI2-kd rice plants compared with wild-type rice and, of these, approximately 39% were BTH responsive. Taken together, our results suggest that induction of SA-responsive genes, including WRKY45, is likely responsible for enhanced disease resistance in OsSSI2-kd rice plants.
Jiang
Chang-Jie
CJ
Plant Disease Resistance Research Unit, Division of Plant Science, National Institute of Agrobiological Sciences, Tsukuba, Japan.
Shimono
Masaki
M
Maeda
Satoru
S
Inoue
Haruhiko
H
Mori
Masaki
M
Hasegawa
Morifumi
M
Sugano
Shoji
S
Takatsuji
Hiroshi
H
D044943:Fatty Acid Desaturases / Q000235:genetics / Q000502:physiology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005990:Glycerol / Q000494:pharmacology; D007113:Immunity, Innate / Q000235:genetics; D020082:Magnaporthe / Q000502:physiology; D005810:Multigene Family; D020411:Oligonucleotide Array Sequence Analysis; D012275:Oryza / Q000187:drug effects / Q000201:enzymology* / Q000382:microbiology / Q000502:physiology; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D020156:Salicylic Acid / Q000378:metabolism; D014974:Xanthomonas / Q000502:physiology
D010940:Plant Proteins; D044943:Fatty Acid Desaturases; D020156:Salicylic Acid; D005990:Glycerol