FIGURE 2 | Interactions between ethylene,abscisic acid,and
nitric oxide signaling pathways in the regulation of seed
germination and dormancy. This schemeis based on genetic
analyses,microarray data,and physiological studies on seed
responsiveness to ABA,ethylene,or NO.ABA binding to PYR/PYL/RCAR
receptor induces the formation faprotein complex with PP2C and the
inhibition of phosphatase activity.In the absence of ABA,PP2C
dephosphorylate SnRK2. When ABA is present, PP2C binding to there ceptor
releases inhibition of SnRK2 activity,which canphosphory late downstream
targets, including ABI5-related transcription factors. Interactions between
ABI3 and ABI5 mediate transcription a lregulation of ABA-respon sivegenes.
Ethylene positively regulates its own biosynthesis,by acting on ACC
synthesis catalyzed by AC Sand subsequent conversion to ethylene by ACO.
This last stepisalsosub jectto ABA inhibition. Ethylene is perceived by
receptors (amongwhichETR1) located in the endoplasmicreticulum;its
binding leadstothedeactivationofthereceptorsthatbecomeenableto
recruitCTR1.ReleaseofCTR1inhibitionallowsEIN2toactasapositive