TY - JOUR

T1 - Arabidopsis phytochrome a is modularly structured to integrate the multiple features that are required for a highly sensitized phytochrome

AU - Oka, Yoshito

AU - Ono, Yuya

AU - Toledo-Ortiz, Gabriela

AU - Kokaji, Keio

AU - Matsui, Minami

AU - Mochizuki, Nobuyoshi

AU - Nagatani, Akira

PY - 2012/7

Y1 - 2012/7

N2 - Phytochrome is a red (R)/far-red (FR) light-sensing photoreceptor that regulates various aspects of plant development. Among the members of the phytochrome family, phytochrome A (phyA) exclusively mediates atypical phytochrome responses, such as the FR high irradiance response (FR-HIR), which is elicited under prolonged FR. A proteasome-based degradation pathway rapidly eliminates active Pfr (the FR-absorbing form of phyA) under R. To elucidate the structural basis for the phyA-specific properties, we systematically constructed 16 chimeric phytochromes in which each of four parts of the phytochrome molecule, namely, the N-terminal extension plus the Per/Arnt/Sim domain (N-PAS), the cGMP phosphodiesterase/adenyl cyclase/FhlA domain (GAF), the phytochrome domain (PHY), and the entire C-terminal half, was occupied by either the phyA or phytochrome B sequence. These phytochromes were expressed in transgenic Arabidopsis thaliana to examine their physiological activities. Consequently, the phyA N-PAS sequence was shown to be necessary and sufficient to promote nuclear accumulation under FR, whereas the phyA sequence in PHY was additionally required to exhibit FR-HIR. Furthermore, the phyA sequence in PHY alone substantially increased the light sensitivity to R. In addition, the GAF phyA sequence was important for rapid Pfr degradation. In summary, distinct structural modules, each of which confers different properties to phyA, are assembled on the phyA molecule.

AB - Phytochrome is a red (R)/far-red (FR) light-sensing photoreceptor that regulates various aspects of plant development. Among the members of the phytochrome family, phytochrome A (phyA) exclusively mediates atypical phytochrome responses, such as the FR high irradiance response (FR-HIR), which is elicited under prolonged FR. A proteasome-based degradation pathway rapidly eliminates active Pfr (the FR-absorbing form of phyA) under R. To elucidate the structural basis for the phyA-specific properties, we systematically constructed 16 chimeric phytochromes in which each of four parts of the phytochrome molecule, namely, the N-terminal extension plus the Per/Arnt/Sim domain (N-PAS), the cGMP phosphodiesterase/adenyl cyclase/FhlA domain (GAF), the phytochrome domain (PHY), and the entire C-terminal half, was occupied by either the phyA or phytochrome B sequence. These phytochromes were expressed in transgenic Arabidopsis thaliana to examine their physiological activities. Consequently, the phyA N-PAS sequence was shown to be necessary and sufficient to promote nuclear accumulation under FR, whereas the phyA sequence in PHY was additionally required to exhibit FR-HIR. Furthermore, the phyA sequence in PHY alone substantially increased the light sensitivity to R. In addition, the GAF phyA sequence was important for rapid Pfr degradation. In summary, distinct structural modules, each of which confers different properties to phyA, are assembled on the phyA molecule.

KW - Arabidopsis

KW - Arabidopsis Proteins

KW - Cell Nucleus

KW - Darkness

KW - Hypocotyl

KW - Light

KW - Mutation

KW - Phytochrome A

KW - Phytochrome B

KW - Plants, Genetically Modified

KW - Protein Structure, Tertiary

KW - Recombinant Fusion Proteins

KW - Seedlings

U2 - 10.1105/tpc.111.094201

DO - 10.1105/tpc.111.094201

M3 - Journal article

C2 - 22843485

VL - 24

SP - 2949

EP - 2962

JO - Plant Cell

JF - Plant Cell

SN - 1040-4651

IS - 7

ER -