Phytochrome and retrograde signalling pathways converge to antagonistically regulate a light-induced transcriptional network.

Plastid-to-nucleus retrograde signals emitted by dysfunctional chloroplasts impact photomorphogenic development, but the molecular link between retrograde- and photosensory-receptor signalling has remained unclear. Here, we show that the phytochrome and retrograde signalling (RS) pathways converge antagonistically to regulate the expression of the nuclear-encoded transcription factor GLK1, a key regulator of a light-induced transcriptional network central to photomorphogenesis. GLK1 gene transcription is directly repressed by PHYTOCHROME-INTERACTING FACTOR (PIF)-class bHLH transcription factors in darkness, but light-activated phytochrome reverses this activity, thereby inducing expression.

The maize Dof protein PBF activates transcription of gamma-zein during maize seed development.

Maize PBF (prolamin-box binding factor) belongs to the Dof class of plant specific transcription factors containing one highly conserved zinc finger DNA-binding domain, called Dof (DNA binding with one finger) domain. Maize PBF trans-activates the gamma-zein gene (gammaZ) promoter in developing maize seeds as shown by transient expression in maize endosperms. Co-transfection of a gammaZ:GUS construct with 35S:PBF resulted in a sevenfold increase in GUS expression, however, PBF mutation in Cys residues within the Dof domain abolishes both, binding to DNA and the capacity to activate gammaZ promoter.

The fuc1 gene product (20 kDa FUC1) of Pisum sativum has no alpha-L-fucosidase activity.

An alpha-L-fucosidase purified from pea (Pisum sativum L. cv Alaska) epicotyl was previously described as a cell wall enzyme of 20 kDa that hydrolyses terminal alpha-L-fucosidic linkages from oligosaccharide fragments of xyloglucan. cDNA and genomic copies were further isolated and sequenced.