A Plant Cryptochrome Controls Key Features of the Chlamydomonas Circadian Clock and Its Life Cycle

Abstract

Cryptochromes are flavin-binding proteins that act as blue light receptors in bacteria, fungi, plants, and insects and are components of the circadian oscillator in mammals. Animal and plant cryptochromes are evolutionarily divergent, although the unicellular alga ( throughout) has both an animal-like cryptochrome and a plant cryptochrome (pCRY; formerly designated CPH1). Here, we show that the pCRY protein accumulates at night as part of a complex. Functional characterization of pCRY was performed based on an insertional mutant that expresses only 11% of the wild-type pCRY level. The mutant is defective for central properties of the circadian clock. In the mutant, the period is lengthened significantly, ultimately resulting in arrhythmicity, while blue light-based phase shifts show large deviations from what is observed in wild-type cells. We also show that pCRY is involved in gametogenesis in pCRY is down-regulated in pregametes and gametes, and in the mutant, there is altered transcript accumulation under blue light of the strictly light-dependent, gamete-specific gene pCRY acts as a negative regulator for the induction of mating ability in the light and for the loss of mating ability in the dark. Moreover, pCRY is necessary for light-dependent germination, during which the zygote undergoes meiosis that gives rise to four vegetative cells. In sum, our data demonstrate that pCRY is a key blue light receptor in that is involved in both circadian timing and life cycle progression.

Chemical and Sensory Properties of Greenhouse Tomatoes Remain Unchanged in Response to Red, Blue, and Far Red Supplemental Light from Light-emitting Diodes

“…In other plant species, environmental conditions, including light quality and quantity, have been shown to modulate the levels of antioxidant compounds measured in our studies (Tables 3 and 4) as mediated by the phytochrome and cryptochrome photoreceptor families (Alba et al, 2000;Beggs et al, 1987;Duell-Pfaff and Wellmann, 1982;M€ uller et al, 2017;Oelm€ uller and Mohr, 1985). Overexpression of CRYPTOCHROME 2 (CRY2), one of three blue/ultraviolet-A sensing cryptochromes found in tomato plants, greatly increased flavonoids and carotenoids in fruit tissues showing a direct link between blue light perception and phytochemical biosynthesis (Giliberto et al, 2005).…”

A Series of Fortunate Events: Introducing Chlamydomonas as a Reference Organism

“…Therefore, under diurnal conditions, cells lack cilia at night but synthesize them anew before the next dawn ( Figure 3A; Cross and Umen, 2015;Zones et al, 2015;Strenkert et al, 2019). Algae such as C. reinhardtii possess a circadian clock that shares some similarity with known Arabidopsis clock components, which generate oscillations with strong amplitudes and help synchronize cellular metabolism and cell division to imposed diurnal cycles (Matsuo et al, 2008;Noordally and Millar, 2015;Müller et al, 2017). Biosynthetic pathways for classical phytohormones are present in most algae, but the genes encoding their associated receptors are mostly missing from algal genomes (Lu and Xu, 2015;Wang et al, 2015a).…”

“…The isolation and manipulation of zygotes are facilitated by plating mating mixtures on 4% agar plates, as zygotes adhere strongly to the surface of this medium. Zygotes are later induced to germinate (undergo meiosis) via transfer onto rich medium in the light, which is perceived by the blue light photoreceptors cryptochrome and phototropin (Huang and Beck, 2003;Müller et al, 2017;Zou et al, 2017). Chlamydomonas can be used for tetrad analysis via the dissection of the four germinated meiotic products, as they carry one or the other mating type, which segregate in a 2:2 ratio.…”

Insights into the red algae and eukaryotic evolution from the genome of Porphyra umbilicalis (Bangiophyceae, Rhodophyta)

“…The plant circadian clock contains blue-and red-light photoreceptors, including cryptochromes (CRY) and phytochromes (PHY), to entrain the circadian clock (55,56); these photoreceptors are also involved in other fundamental processes in plants, including growth and development. Porphyra does not appear to encode a PHY photoreceptor or a typical plant CRY photoreceptor, although it has maintained four genes of the CRY/photolyase family.…”