Photophysiology of a Tomato Mutant Deficient in Labile Phytochrome

Overexpression of Phytochrome B Induces a Short Hypocotyl Phenotype in Transgenic Arabidopsis.

“…These overexpression phenotypes complement the long hypocotyl phenotypes observed in photomorphogenic mutants deficient in either phytochrome A or phytochrome B. The long hypocotyl aurea mutant of tomato is deficient in light-labile phytochrome A (Parks et al, 1987) but retains normal levels of light-stable phytochrome (Adamse et al, 1988~). Conversely, based on photobiological studies, it has been proposed that the Ih long hypocotyl mutant of cucumber (Adamse et al, 1987(Adamse et al, , 1988b) and the hy3 long hypocotyl mutant of Arabidopsis are deficient in lightstable phytochrome but have normal levels of light-labile phytochrome (Adamse et al, 1988a).…”

The cucumber long hypocotyl mutant lacks a light-stable PHYB-like phytochrome.

“…It is of interest to ascertain whether such closely related proteins have separate biological roles. An end-of-day, far-red light, stem-growth reaction was exhibited by the au mutant (Adamse et al, 1988b;L6pez-Juez et al, 1990b) but was absent in the Ih mutant (Adamse et al, , 1988aL6pez-Juez et al, 199Oa). This end-of-day far-red treatment depletes active phytochrome during the subsequent dark period and mimics the action of vegetational shade-light.…”

“…Two photomorphogenic mutants that are physiologically very different from each other are the aurea (au) of tomato (Koornneef et al, 1985;Adamse et al, 1988b) and the long hypocotyl (Ih) of cucumber (Adamse et al, , 1988a; their characterization has led to the suggestion of separate functions for the different molecular species of phytochrome (for review, see Kendrick and Nagatani, 1991). It is of interest to ascertain whether such closely related proteins have separate biological roles.…”

Altered Phytochrome Regulation of Greening in an aurea Mutant of Tomato

“…The au mutant line W616 has been used in several recent studies to ask questions about phytochrome action ( 17,21). The au mutant does show phytochrome responses attributable to the low level of stable phytochrome present in light-grown plants, such as promotion of hypocotyl elongation by end-of-day far-red light (1). The light-stable phytochrome pool is presumably little affected by the au mutation (1).…”

“…Seeds were sown in vermiculite soaked with 0.1 mm gibberellic acid A3 (Sigma). The combination of these two methods of enhancing germination (1,21) led to germination rates of at least 80% in wild type and mutant. The addition of gibberellin slightly decreased the greening rate as compared to controls germinated on deionized water alone, but did not affect the extent of potentiation of greening by a red pulse (data not shown).…”