A1 associates with ARF6, a small G protein in host cells which are accessible only when ARF6 is in its active (GTP-bound) form. 

TLS Online TPP Program

#Id: 9813

#XL - R Botany

PHYA is the only gene that encodes a Type I phytochrome and predominantly perceives far-red light.

Phytochrome B predominantly perceives red light

TLS Online TPP Program

#Id: 9814

#XL - R Botany

The PHYA gene is transcriptionally active in dark-grown seedlings, but its expression is strongly inhibited in the light in monocots.

TLS Online TPP Program

#Id: 9815

#XL - R Botany

The PRD domain of phyB serve as an NLS. 

Conversion of Pr to Pfr by red light expose the functional NLS of the PRD domain of phyB, facilitating phyB’s import into the nucleus.

TLS Online TPP Program

#Id: 9816

#XL - R Botany

PRD domain of phyA cannot act as an NLS, so to transport it into the nucleus requires FARRED ELONGATED HYPOCOTYL1 (FHY1) and its homolog FHY1-LIKE (FHL),

TLS Online TPP Program

#Id: 9817

#XL - R Botany

Phytochrome responses fall into three major categories based on the amount of light they require: very low fluence responses (VLFRs), low-fluence responses (LFRs), and high-irradiance responses (HIRs).

TLS Online TPP Program

#Id: 9818

#XL - R Botany

VLFRs are non-photoreversible.