Potato modified for altered phytochrome B expression

Potato plants are modified to consitutively express the phytochrome B gene from Arabidopsis thaliana which codes for a regulatory photoreceptor which exists in two forms that are reversibly interconvertible by light: the Pr form that absorbs maximally in the red region of the spectrum and the Pfr form that absorbs maximally in the far-red region. Photoconversion of Pr to Pfr induces an array of morphogenetic responses, whereas reconversion of Pfr to Pr cancels the induction of those responses.

As a result of the genetic modification, the anthocyanin and chlorophyll synthesis is enhanced and the photosynthesis rate is increased in the transgenic plants. Furthermore, a number of morphological and physiological changes take place, such as reduced apical dominance, shorter internodes, dwarfism, delayed senescence, thicker stems, starch deposits and increased specific weight in the stems and leaves, smaller leaves, elongation of the palisade parenchyma cells, enhanced root formation, increased number of tubers and increased tuber yield.

pMAB316::pTiB6S3-SE

As a major transcription regulator in plants, phytochrome B (PhyB) affects the transcription of a variety of genes. Therefore, while not directly affected by the transformation, the regulation of genes involved in a variety of different physiological and morphological characteristics and metabolic pathways is altered by the elevated PhyB levels in the transgenic plants, such as the phytohormone balance, circadian regulation, regulation of flowering and seed germination, photosynthesis, phototropism and gravitropism, defense responses, the response to cold and the response to visible red and blue light.