Five Phytochromes, Two Cryptochromes, One Phototropin, and One Superchrome The first blue-light receptors to be identified were the two cryptochromes. Cryptochromes are a class of flavoproteins that are sensitive to blue light. They are found in Unlike phytochromes and phototropins, cryptochromes are not kinases. Their flavin chromophore is reduced by light and transported into the cell  ‎Function · ‎Phototropism · ‎Light capture · ‎Circadian rhythm. Phytochromes are a class of photoreceptor in plants, bacteria and fungi use to detect light. Other plant photoreceptors include cryptochromes and phototropins, which respond to blue and ultraviolet-A light and UVR8, which is sensitive to.


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Finally, cry2 and phyB are antagonistic in the induction of flowering.


Consistent with these levels of chlorophyll and gene expression, plastids developed thylakoid membranes preferentially under phytochromes and cryptochromes light Fig. We seldom found plastids with thylakoids in the roots grown under red light, although chlorophyll fluorescence was observed in these conditions Fig.

In contrast to root greening, both red and blue light induce greening in the aerial parts of Arabidopsis seedlings efficiently Neff and Chory Microarray analysis, in which most of the mRNA should be derived from leaves, has suggested that different wavelengths of light trigger largely similar genome phytochromes and cryptochromes profiles Ma et al.


To date, no preferential induction of expression by blue light has been reported for photosynthetic genes. Hence, the regulation mechanism of greening appears to be different between roots and aerial parts.

We further demonstrated that this response was organ autonomous Fig. Involvement of phytochromes and cryptochromes in root greening A low level of root greening in response to red light was mediated by phyB.

Phytochromes and cryptochromes red light, the phyB and phyAphyB double mutants showed no chlorophyll accumulation and photosynthetic gene expression Fig. By contrast, no aberrant phenotype was observed for the phyA single mutant.

These observations fit well with the general concept that phyB acts as the primary photoreceptor under continuous red light Quail In phytochromes and cryptochromes, the involvement of cryptochromes in the red light response was suggested.

The cry1cry2 double mutant showed reduced chlorophyll levels under the light Fig.


We could not observe significant reduction in gene expression Fig. Despite the fact that cryptochromes show no absorption peak in the red region of the spectrum Lin et al.


Therefore, cryptochromes may have some activity even without light activation. Blue light was more effective at promoting root greening. Since it was found that red light alone induced phytochromes and cryptochromes only partially, involvement by blue light photoreceptors was expected.

  • Cryptochrome - Wikipedia
  • Phytochromes, cryptochromes, phototropin: photoreceptor interactions in plants.

Indeed, cryptochromes were involved in this response, and under blue light, the cry1 mutant showed a considerable decrease in chlorophyll content Fig. This indicated that cry1 was the major photoreceptor in this response.

Cryptochromes and phytochromes synergistically regulate Arabidopsis root greening under blue light.

Since the cry2 mutant and cry1cry2 double mutants exhibited lower chlorophyll accumulation than the wild type and the cry1 mutant, respectively Fig. More phytochromes and cryptochromes, either phyA or phyB was required for a high level of root greening under blue light, since the phyAphyB double mutant was totally deficient in chlorophyll accumulation and photosynthetic gene induction under blue light Fig.

The dichromatic irradiation experiment demonstrated that the active PFR form of phyB was required for this synergistic interaction Fig. In the case of phyA, blue light alone was phytochromes and cryptochromes for this synergistic response Fig.


This is consistent with observations that phyA is activated by blue light for various physiological responses Shinomura et al. These observations indicate that phytochromes act as blue light photoreceptors, and that both the phytochrome and cryptochrome systems must phytochromes and cryptochromes activated for a high level of root greening in Arabidopsis.

Phytochrome - Wikipedia

This type of synergism between phytochrome and blue light photoreceptors has been reported in several other responses see phytochromes and cryptochromes. It should be noted here that an angiosperm enzyme that catalyzes the reduction of protochlorophyllide to chlorophyllide requires light for reaction.

phytochromes and cryptochromes However, this reaction was probably not the rate-limiting step under the conditions tested. Both blue and red light are effective in this enzymatic reaction Koski et al.

Cryptochromes and phytochromes synergistically regulate Arabidopsis root greening under blue light.

Dichromatic irradiation experiments phytochromes and cryptochromes that this interaction depends on the level of phyB P FR.

Analysis of the cop1, det1 and hy5 mutants indicated that the corresponding factors were involved in the response. Their flavin chromophore is reduced by light and transported into the cell nucleuswhere it affects the turgor pressure and causes subsequent stem elongation.