Arabidopsis thaliana life without phytochromes

STRASSER, B; SANCHEZ-LAMAS, M; YANOVSKY, MJ; CASAL, JJ; CERDAN, P

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA

NATL ACAD SCIENCES

Año: 2010 vol. 107 p. 4776 - 4781

0027-8424

Plants use light as a source of energy for photosynthesis and as asource of environmental information perceived by photoreceptors.Testing whether plants can complete their cycle if lightprovides energy but no information about the environmentrequires a plant devoid of phytochromes because all photosyntheticallyactive wavelengths activate phytochromes. Producingsuch a quintuple mutant of Arabidopsis thaliana has beenchallenging, but we were able to obtain it in the flowering locusT (ft) mutant background. The quintuple phytochrome mutantdoes not germinate in the FT background, but it germinates tosome extent in the ft background. If germination problems arebypassed by the addition of gibberellins, the seedlings of thequintuple phytochrome mutant exposed to red light producechlorophyll, indicating that phytochromes are not the sole redlightphotoreceptors, but they become developmentally arrestedshortly after the cotyledon stage. Blue light bypasses this blockage,rejecting the long-standing idea that the blue-light receptorscryptochromes cannot operate without phytochromes. Aftergrowth under white light, returning the quintuple phytochromemutant to red light resulted in rapid senescence of alreadyexpanded leaves and severely impaired expansion of new leaves.We conclude that Arabidopsis development is stalled at severalpoints in the presence of light suitable for photosynthesis butproviding no photomorphogenic signal.