Reverse‐genetic approach to verify physiological roles of rice phytoalexins: characterization of a knockdown mutant of OsCPS4 phytoalexin biosynthetic gene in rice. Issue 1 (10th June 2013)

• Record Type: Journal Article
• Authors: Toyomasu, Tomonobu; Usui, Masami; Sugawara, Chizu; Otomo, Kazuko; Hirose, Yuko; Miyao, Akio; Hirochika, Hirohiko; Okada, Kazunori; Shimizu, Takafumi; Koga, Jinichiro; Hasegawa, Morifumi; Chuba, Masaru; Kawana, Yoshiaki; Kuroda, Masaharu; Minami, Eiichi; Mitsuhashi, Wataru; Yamane, Hisakazu
• Is Part Of: Physiologia plantarum. Volume 150:Issue 1(2014:Jan.)
• Page Start: 55
• Page End: 62
• Publication Date: 2013-06-10
• Subjects: Plant physiology -- Periodicals; 571.2
• DOI: 10.1111/ppl.12066
• Languages: English
• ISSNs: 0031-9317

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>A variety of labdane‐related diterpenoids, including phytocassanes, oryzalexins and momilactones, were identified as phytoalexins in rice (<italic>Oryza sativa</italic> L.). Momilactone B was also isolated as an allelochemical exuded from rice roots. The biosynthetic genes of these phytoalexins have been identified, including six labdane‐related diterpene cyclase genes such as <italic>OsCPS2</italic>, <italic>OsCPS4</italic>, <italic>OsKSL4</italic>, <italic>OsKSL7</italic>, <italic>OsKSL8</italic> and <italic>OsKSL10</italic>. Here we identified an <italic>OsCPS4</italic> knockdown mutant, <italic>cps4‐tos</italic>, by screening <italic>Tos17</italic> mutant lines using polymerase chain reaction. <italic>OsCPS4</italic> encodes a <italic>syn</italic>‐copalyl diphosphate synthase responsible for momilactones and oryzalexin S biosynthesis. Because <italic>Tos17</italic> was inserted into the third intron of <italic>OsCPS4</italic>, the mature <italic>OsCPS4</italic> mRNA was detected in the <italic>cps4‐tos</italic> mutant as well as the wild type. Nevertheless, mature <italic>OsCPS4</italic> transcript levels in the <italic>cps4‐tos</italic> mutant were about one sixth those in the wild type. The <italic>cps4‐tos</italic> mutant was more susceptible to rice blast fungus than the wild type, possibly due to lower levels of momilactones and oryzalexin S in the mutant. Moreover, co‐cultivation experiments suggested that the allelopathic effect of <italic>cps4‐tos</italic> against some kinds of lowland weeds was significantly lower than that of the wild type, probably because of lower momilactone content exuded from <italic>cps4‐tos</italic> roots. A reverse‐genetic strategy using the <italic>cps4‐tos</italic> mutant showed the possible roles of momilactones not only as phytoalexins but also as allelopathic substances.</p> </abstract>