Diterpenoid phytoalexin factor, a bHLH transcription factor, plays a central role in the biosynthesis of diterpenoid phytoalexins in rice

Abstract

SUMMARYRice (Oryza sativa) produces diterpenoid phytoalexins (DPs), momilactones and phytocassanes as major phytoalexins. Accumulation of DPs is induced in rice by blast fungus infection, copper chloride or UV light. Here, we describe a rice transcription factor named diterpenoid phytoalexin factor (DPF), which is a basic helix-loop-helix (bHLH) transcription factor. The gene encoding DPF is expressed mainly in roots and panicles, and is inducible in leaves by blast infection, copper chloride or UV. Expression of all DP biosynthetic genes and accumulation of momilactones and phytocassanes were remarkably increased and decreased in DPF over-expressing and DPF knockdown rice, respectively. These results clearly demonstrated that DPF positively regulates DP accumulation via transcriptional regulation of DP biosynthetic genes, and plays a central role in the biosynthesis of DPs in rice. Furthermore, DPF activated the promoters of COPALYL DIPHO-SPHATE SYNTHASE2 (CPS2) and CYTOCHROME P450 MONOOXYGENASE 99A2 (CYP99A2), whose products are implicated in the biosynthesis of phytocassanes and momilactones, respectively. Mutations in the Nboxes in the CPS2 upstream region, to which several animal bHLH transcription factors bind, decreased CPS2 transcription, indicating that DPF positively regulates CPS2 transcription through the N-boxes. In addition, DPF partly regulates CYP99A2 through the N-box. This study demonstrates that DPF acts as a master transcription factor in DP biosynthesis.

Integration of danger peptide signals with herbivore‐associated molecular pattern signaling amplifies anti‐herbivore defense responses in rice

“…Similar enhancements were observed in the induction of transcripts for KAURENE SYNTHASE‐LIKE 4 ( OsKSL4 ) and diterpenoid phytoalexin factor ( DPF ) 3 h after simultaneous application of OS MYL /HME and OsPep3 (Figure S3). As the enzymes encoded by these genes mediate rate‐limiting steps in momilactone biosynthesis (Yamamura et al ., ), OsPep3 is likely to activate MB biosynthesis rather than inhibit its degradation, although this needs to be further tested. Taken together, our data suggest that a DAMP derived from the wound‐ and OS MYL ‐inducible protein OsPROPEP3 promotes defense metabolism in rice.…”

Identification of two transcription factors activating the expression of OsXIP in rice defence response

“…Some bHLH transcription factors in rice are involved in stress responses. For instance, RERJ1 (OsbHLH006) responded to wound and drought [34, 35]; OsBP-5 (OsbHLH102) is related to transcriptional regulation of the rice Wx gene [36]; OsbHLH094 forms a complex with RSS3 and JASMONATE ZIM-DOMAIN (JAZ) proteins to modulate the expression of JA-responsive genes [37]; DPF (OsbHLH25) positively regulates the accumulation of diterpenoid phytoalexins [38]. …”

OsMYC2, an essential factor for JA-inductive sakuranetin production in rice, interacts with MYC2-like proteins that enhance its transactivation ability

“…In particular, several TFs have been well-studied and reported to contribute to the production of diterpenoid phytoalexins or expression of their biosynthetic genes in rice15161718. However, regulatory factors responsible for sakuranetin production and/or OsNOMT expression remain unclear.…”