Striga parasitizes major crops in arid regions, depriving the host crop of nutrients through the transpiration stream and causing vast agricultural damage. Here, we report on the mechanism underlying how Striga maintains high transpiration under drought conditions. We found that Striga did not respond to abscisic acid, the phytohormone responsible for controlling stomatal closure. Protein phosphatase 2C of Striga (ShPP2C1) is not regulated by abscisic acid receptors, and this feature is attributable to specific mutations in its amino acid sequence. Moreover, Arabidopsis transformed with ShPP2C1 showed an abscisic acid-insensitive phenotype, indicating that ShPP2C1 functions as a dominant negative regulator of abscisic acid signal transduction. These findings suggest that ShPP2C1 interrupts abscisic acid signalling in Striga, resulting in high transpiration and subsequent efficient absorption of host nutrients under drought conditions.
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The RNA sequencing data have been deposited at the DNA Databank of Japan under accession codes DRX142184, DRX142185. Complementary DNAs were registered at the DNA Databank of Japan with accession numbers as follows: ShPYL1, LC377366; ShPYL2, LC377367; ShPYL3, LC377368; ShPYL4, LC377369; ShPYL5, LC377370; ShPYL6, LC377371; ShPYL7, LC377372; ShPYL8, LC377373; ShPP2C1, LC377362; ShPP2C2, LC377363; ShPP2C3, LC377364; ShPP2C4, LC377365. Other data that support the findings of this study are available from the corresponding author on reasonable request.
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We thank A.G.T. Babiker for providing Striga seeds. We also thank T. Hosouchi and S. Shinpo for technical support in Illumina sequencing; N. Arimoto, M. Negishi and Y. Yamakawa for supporting transgenic Arabidopsis experiments; Y. Tsuchiya and K. Hanada for advising on identification of the ABA receptor and PP2C from Striga; and T. Hirayama for providing the Columbia accession background Arabidopsis abi1c mutant. This work was supported by grants from MEXT/JSPS KAKENHI (No. 17H05009 to M.O., No. 15H05248 to Y.S.), MEXT/JSPS Bilateral Programs (to Y.S.), the Joint Research Program of Arid Land Research Center, Tottori University (No. 28C2004 to Y.S.) and Japan Science and Technology Agency (PRESTO, No. JPMJPR15Q5 to M.O.); and the SATREPS Striga project to Y.S.
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Scientific Reports (2019)