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Small‐molecule auxin inhibitors that target YUCCA are powerful tools for studying auxin function
Author(s) -
Kakei Yusuke,
Yamazaki Chiaki,
Suzuki Masashi,
Nakamura Ayako,
Sato Akiko,
Ishida Yosuke,
Kikuchi Rie,
Higashi Shouichi,
Kokudo Yumiko,
Ishii Takahiro,
Soeno Kazuo,
Shimada Yukihisa
Publication year - 2015
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.13032
Subject(s) - auxin , yucca , biochemistry , arabidopsis thaliana , arabidopsis , mutant , function (biology) , chemistry , coleoptile , indole 3 acetic acid , microbiology and biotechnology , biology , gene , botany
Summary Auxin is essential for plant growth and development, this makes it difficult to study the biological function of auxin using auxin‐deficient mutants. Chemical genetics have the potential to overcome this difficulty by temporally reducing the auxin function using inhibitors. Recently, the indole‐3‐pyruvate ( IP yA) pathway was suggested to be a major biosynthesis pathway in Arabidopsis thaliana L. for indole‐3‐acetic acid ( IAA ), the most common member of the auxin family. In this pathway, YUCCA , a flavin‐containing monooxygenase ( YUC ), catalyzes the last step of conversion from IP yA to IAA . In this study, we screened effective inhibitors, 4‐biphenylboronic acid ( BB o) and 4‐phenoxyphenylboronic acid ( PPB o), which target YUC . These compounds inhibited the activity of recombinant YUC in vitro , reduced endogenous IAA content, and inhibited primary root elongation and lateral root formation in wild‐type Arabidopsis seedlings. Co‐treatment with IAA reduced the inhibitory effects. Kinetic studies of BB o and PPB o showed that they are competitive inhibitors of the substrate IP yA. Inhibition constants ( K i ) of BB o and PPB o were 67 and 56 n m , respectively. In addition, PPB o did not interfere with the auxin response of auxin‐marker genes when it was co‐treated with IAA , suggesting that PPB o is not an inhibitor of auxin sensing or signaling. We propose that these compounds are a class of auxin biosynthesis inhibitors that target YUC . These small molecules are powerful tools for the chemical genetic analysis of auxin function.