The Full-Size ABCG Transporters Nb-ABCG1 and Nb-ABCG2 Function in Pre- and Postinvasion Defense against Phytophthora infestans in Nicotiana benthamiana

• Published in: The Plant cell 2016-05, Vol.28 (5), p.1163-1181
• Main Authors: Shibata, Yusuke, Ojika, Makoto, Sugiyama, Akifumi, Yazaki, Kazufumi, Jones, David A., Kawakita, Kazuhito, Takemoto, Daigo
• Format: Article
• Language: English
• Subjects: ATP Binding Cassette Transporter, Subfamily G - genetics; ATP Binding Cassette Transporter, Subfamily G - metabolism; Capsicum; Gene Expression Regulation, Plant - genetics; Nicotiana; Nicotiana - genetics; Nicotiana - metabolism; Nicotiana - microbiology; Nicotiana benthamiana; Phytophthora infestans; Phytophthora infestans - pathogenicity; Plant Diseases - genetics; Plant Diseases - microbiology; Plant Proteins - genetics; Plant Proteins - metabolism; Solanum tuberosum
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.15.00721

The sesquiterpenoid capsidiol is the major phytoalexin produced by Nicotiana and Capsicum species. Capsidiol is produced in plant tissues attacked by pathogens and plays a major role in postinvasion defense by inhibiting pathogen growth. Using virus-induced gene silencing-based screening, we identified two Nicotiana benthamiana (wild tobacco) genes encoding functionally redundant full-size ABCG (PDR-type) transporters, Nb-ABCG1/PDR1 and Nb-ABCG2/PDR2, which are essential for resistance to the potato late blight pathogen Phytophthora infestans. Silencing of Nb-ABCG1/2 compromised secretion of capsidiol, revealing Nb-ABCG1/2 as probable exporters of capsidiol. Accumulation of plasma membrane-localized Nb-ABCG1 and Nb-ABCG2 was observed at the site of pathogen penetration. Silencing of EAS (encoding 5-epi-aristolochene synthase), a gene for capsidiol biosynthesis, reduced resistance to P. infestans, but penetration by P. infestans was not affected. By contrast, Nb-ABCG1/2-silenced plants showed reduced penetration defense, indicating that Nb-ABCG1/2 are involved in preinvasion defense against P. infestans. Plastidic GGPPS1 (geranylgeranyl diphosphate synthase) was also found to be required for preinvasion defense, thereby suggesting that plastid-produced diterpene(s) are the antimicrobial compounds active in preinvasion defense. These findings suggest that N. benthamiana ABCG1/2 are involved in the export of both antimicrobial diterpene(s) for preinvasion defense and capsidiol for postinvasion defense against P. infestans.