Phytochrome B and at Least One Other Phytochrome Mediate the Accelerated Flowering Response of Arabidopsis thaliana L. to Low Red/Far-Red Ratio.

AUTOR(ES)

Halliday, K. J.

RESUMO

We have investigated the involvement of phytochrome B in the early-flowering response of Arabidopsis thaliana L. seedlings to low red:far-red (R/FR) ratio light conditions. The phytochrome B-deficient hy3 (phyB) mutant is early flowering, and in this regard it resembles the shade-avoidance phenotype of its isogenic wild type. Seedlings carrying the hy2 mutation, resulting in a deficiency of phytochrome chromophore and hence of active phytochromes, also flower earlier than wild-type plants. Whereas hy3 or hy2 seedlings show only a slight acceleration of flowering in response to low R/FR ratio, seedlings that are doubly homozygous for both mutations flower earlier than seedlings carrying either phytochrome-related mutation alone. This additive effect clearly indicates the involvement of one or more phytochrome species in addition to phytochrome B in the flowering response as well as indicating the presence of some functional phytochrome B in hy2 seedlings. Seedlings that are homozygous for the hy3 mutation and one of the fca, fwa, or co late-flowering mutations display a pronounced early-flowering response to low R/FR ratio. A similar response to low R/FR ratio is displayed by seedlings doubly homozygous for the hy2 mutation and any one of the late-flowering mutations. Thus, placing the hy3 or hy2 mutations into a late-flowering background has the effect of uncovering a flowering response to low R/FR ratio. Seedlings that are triply homozygous for the hy3, hy2 mutations and a late-flowering mutation flower earlier than the double mutants and do not respond to low R/FR ratio. Thus, the observed flowering responses to low R/FR ratio in phytochrome B-deficient mutants can be attributed to the action of at least one other phytochrome species.

Documentos Relacionados

• Mutations in the gene for the red/far-red light receptor phytochrome B alter cell elongation and physiological responses throughout Arabidopsis development.
• A deletion in the PHYD gene of the Arabidopsis Wassilewskija ecotype defines a role for phytochrome D in red/far-red light sensing.
• Regulation of Arabidopsis thaliana L. (Heyn) cor78 in response to low temperature.
• Red/far-red and blue light-responsive regions of maize rbcS-m3 are active in bundle sheath and mesophyll cells, respectively.
• Flowering responses to altered expression of phytochrome in mutants and transgenic lines of Arabidopsis thaliana (L.) Heynh.