Mutation of SPOTTED LEAF3 (SPL3) impairs abscisic acid-responsive signalling and delays leaf senescence in rice.
Lesion mimic mutants commonly display spontaneous cell death in pre-senescent green leaves under normal conditions, without pathogen attack. Despite molecular and phenotypic characterization of several lesion mimic mutants, the mechanisms of the spontaneous formation of cell death lesions remain largely unknown. Here, the rice lesion mimic mutant spotted leaf3 (spl3) was examined. When grown under a light/dark cycle, the spl3 mutant appeared similar to wild-type at early developmental stages, but lesions gradually appeared in the mature leaves close to heading stage. By contrast, in spl3 mutants grown under continuous light, severe cell death lesions formed in developing leaves, even at the seedling stage. Histochemical analysis showed that hydrogen peroxide accumulated in the mutant, likely causing the cell death phenotype. By map-based cloning and complementation, it was shown that a 1-bp deletion in the first exon of Oryza sativa Mitogen-Activated Protein Kinase Kinase Kinase1 (OsMAPKKK1)/OsEDR1/OsACDR1 causes the spl3 mutant phenotype. The spl3 mutant was found to be insensitive to abscisic acid (ABA), showing normal root growth in ABA-containing media and delayed leaf yellowing during dark-induced and natural senescence. Expression of ABA signalling-associated genes was also less responsive to ABA treatment in the mutant. Furthermore, the spl3 mutant had lower transcript levels and activities of catalases, which scavenge hydrogen peroxide, probably due to impairment of ABA-responsive signalling. Finally, a possible molecular mechanism of lesion formation in the mature leaves of spl3 mutant is discussed.
Department of Plant Science, Plant Genomics and Breeding Institute, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea.
Seung-Hyun
SH
Wang
Department of Plant Science, Plant Genomics and Breeding Institute, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea.
Jung-Hyun
JH
Lim
Department of Plant Science, Plant Genomics and Breeding Institute, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea.
Sang-Sook
SS
Kim
Department of Plant Science, Plant Genomics and Breeding Institute, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea.
Sung-Hwan
SH
Cho
Department of Plant Life and Environmental Science, Hankyong National University, Ansung 456-749, Korea.
Soo-Cheul
SC
Yoo
Department of Plant Science, Plant Genomics and Breeding Institute, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea.
Hee-Jong
HJ
Koh
Department of Plant Science, Plant Genomics and Breeding Institute, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea sakuraba0425@gmail.com ncpaek@snu.ac.kr.
Yasuhito
Y
Sakuraba
Department of Plant Science, Plant Genomics and Breeding Institute, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea Crop Biotechnology Institute, GreenBio Science and Technology, Seoul National University, Pyeongchang 232-916, Korea sakuraba0425@gmail.com ncpaek@snu.ac.kr.
Nam-Chon
http://orcid.org/0000-0002-9827-2287
NC
Paek
D000040:Abscisic Acid / Q000378:metabolism*; D002374:Catalase / Q000096:biosynthesis; D016923:Cell Death; D016922:Cellular Senescence; D003001:Cloning, Molecular; D015536:Down-Regulation; D017343:Genes, Plant; D048728:MAP Kinase Kinase Kinase 1 / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D012275:Oryza / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction
D010940:Plant Proteins; D017382:Reactive Oxygen Species; D000040:Abscisic Acid; D002374:Catalase; D048728:MAP Kinase Kinase Kinase 1
Abscisic acid; MAPKKK; catalase activity; lesion mimic mutant; reactive oxygen species; rice; spotted leaf3.