In the dark, PEPCase returns to the inactive form because PEPCase‐kinase is inactivated and a phosphatase releases the phosphoryl group from PEPCase.

TLS Online TPP Program

#Id: 10234

#Unit 6. System Physiology – Plant

BRI1–BAK1-BR-→ BSK--→BSU1--→degradation of Phosphorylated BIN2-----→activation of BES1 & BZR1--→BR Response

TLS Online TPP Program

#Id: 10235

#Unit 6. System Physiology – Plant

Brassinosteroids, like gibberellins, suppress photomorphogenesis in the dark.

TLS Online TPP Program

#Id: 10236

#Unit 6. System Physiology – Plant

DE-ETIOLATED2 (DET2) gene, which encodes a brassinosteroid biosynthetic gene. Det2 loss-of-function mutants have reduced levels of brassinosteroids, resulting in a de-etiolated appearance of the seedling even when grown in the dark

TLS Online TPP Program

#Id: 10237

#Unit 6. System Physiology – Plant

Brassinosteroids are also required for promotion of cell

elongation by gibberellins, and gibberellin-induced degradation

of the DELLA repressor enhances the brassinosteroid response.

TLS Online TPP Program

#Id: 10238

#Unit 6. System Physiology – Plant

OsGSR1, a member of the gibberellic acid–stimulated gene family, acts as a positive regulator of both the gibberellic acid response and brassinosteroid biosynthesis.

TLS Online TPP Program

#Id: 10239

#Unit 6. System Physiology – Plant

ABA was originally thought to induce abscission, however, abscission is regulated by ethylene rather than ABA.