Black spot disease is one of the most serious diseases in Asian pear cultivation, with the commercial cultivar Nijisseiki being susceptible. Ethylene is known to play major roles in regulating plant defense responses against various pathogens. We investigated the relationship between ethylene synthesis and black spot disease in ‘Nijisseiki’ pear leaves by treatment with an analog of ethylene and 1-methylcyclopropene (1-MCP), an inhibitor of ethylene action. Interestingly, both treatments enhanced black spot disease symptoms. Both treatments also increased ethylene production in accordance with disease symptoms through altered gene expression of ethylene biosynthetic enzymes, especially 1-aminocyclopropane-1-carboxylate (ACC) synthase genes (PpACS3 and 4). Chemical names used: 1-methylcyclopropene (1-MCP), 1-aminocyclopropane-1-carboxylate (ACC).
Akihiro Itai, Takaaki Igori, Naoko Fujita, Mayumi Egusa, Motoichiro Kodama, and Hideki Murayama
Ryutaro Tao, Hisayo Yamane, Akira Sugiura, Hideki Murayama, Hidenori Sassa, and Hitoshi Mori
This report identifies S-RNases of sweet cherry (Prunus avium L.) and presents information about cDNA sequences encoding the S-RNases, which leads to the development of a molecular typing system for S-alleles in this fruit tree species. Stylar proteins of sweet cherry were surveyed by two dimensional polyaclylamide gel electrophoresis (2D-PAGE) to identify S-proteins associated with gametophytic self-incompatibility. Glycoprotein spots linked to S-alleles were found in a group of proteins which had Mr and pI similar to those of other rosaceous S-RNases. These glycoproteins were present at highest concentration in the upper segment of the mature style and shared immunological characteristics and N-terminal sequences with those of S-RNases of other plant species. cDNAs encoding these glycoproteins were cloned based on the N-terminal sequences. Genomic DNA and RNA blot analyses and deduced amino acid sequences indicated that the cDNAs encode S-RNases; thus the S-proteins identified by 2D-PAGE are S-RNases. Although S1 to S6-alleles of sweet cherry cultivars could be distinguished from each other with the genomic DNA blot analysis, a much simpler method of PCR-based typing system was developed for the six S-alleles based on the DNA sequence data obtained from the cDNAs encoding S-RNases.