Multiple bHLH Proteins form Heterodimers to Mediate CRY2-Dependent Regulation of Flowering-Time in Arabidopsis

Wang

Proc. Natl. Acad. Sci. U.S.A.

et al. 2013

Self Cite

Significance Plants rely on many different types of photoreceptors to control light responses, but the molecular mechanisms underlying the coaction of different photoreceptors that regulate the same light response remains unclear. This study demonstrates a mechanism of the photoreceptor coaction. In Arabidopsis , the blue-light receptor cryptochrome 2 interacts with and activates the transcription factor CRYPTOCHROME-INTERACTING basic helix–loop–helix 1 (CIB1). It was found that CIB1 protein is degraded in the absence of blue light and that the light–oxygen–voltage-domain F-box blue-light receptor ZEITLUPE mediates blue-light suppression of CIB1 degradation.

Section: Discussionmentioning

confidence: 99%

Arabidopsis CRY2 and ZTL mediate blue-light regulation of the transcription factor CIB1 by distinct mechanisms

Wang

Proc. Natl. Acad. Sci. U.S.A.

et al. 2013

Self Cite

“…Other transcription factors, CIBs (CIB1, CIB2, CIB4, and CIB5), redundantly activate FT expression (Liu et al, 2008a(Liu et al, , 2013c. CIBs form various combinations of heterodimers that possess higher affinities to E-box sequences (CANNTG).…”

Section: Transcriptional Regulation Of Ftmentioning

confidence: 99%

Circadian Clock and Photoperiodic Flowering in Arabidopsis: CONSTANS Is a Hub for Signal Integration

2016

Plants sense changes in day length (= photoperiod) as a reliable seasonal cue to regulate important developmental transitions such as flowering. Integration of various external light information into the circadian clock-controlled mechanisms enables plants to precisely measure photoperiod changes in the surrounding environment. The core mechanism of photoperiodic measurement is regulation of CONSTANS (CO) activity, which takes place in phloem companion cells in leaves. Until recently, it remained unclear whether plants possess specific variations of the clock for this regulation. Now it is known that a specific circadian timing mechanism in the vascular tissue is essential for photoperiodic flowering. In addition to spatial tissue-specific regulation, temporal regulation of CO activity is also important. The identification and characterization of multiple regulators that physically interact with CO and influence its function in the morning in long days are two recent advances in photoperiodic regulation of flowering time. It seems that CO acts as a network hub to integrate various external and internal signals into the photoperiodic flowering pathway. CO regulates the amount of FLOWERING LOCUS T (FT) transcripts and FT protein moves from companion cells of leaf phloem to the shoot apical meristem. The protein that helps long-distance transport of FT protein was also identified recently. Here, we introduce recent advances in tissue-specific variations of the circadian clock and the emerging picture of the intricate connections of transcriptional regulators through CO in the morning, which all facilitate plants knowing when to flower.Properly timing the floral transition is crucial for reproductive success. It can also influence the early development of offspring. To optimize this timing, plants constantly monitor changes in the surrounding environment. Among various environmental factors, observing changes in day length (= photoperiod) is the most reliable way for many organisms to know the specific time of year. Therefore, photoperiodic regulation is one of the major flowering time mechanisms and it has been studied since it was first reported in 1920 (Song et al., 2015). Arabidopsis (Arabidopsis thaliana), as it flowers mainly in spring, can sense lengthening days to induce flowering and became a suitable model to study photoperiodic flowering regulation. (Andrés and Coupland, 2012;Song et al., 2013;Pajoro et al., 2014;Shim and Imaizumi, 2015).In principle, photoperiodic flowering mechanisms can be divided into three parts: light input, circadian clock, and output. Light information is integrated into innate photoperiodic timing mechanisms governed by the circadian clock to induce genes that trigger flowering.

“…This difference in the response to light quality between the ft mutant and the wild type in A. thaliana seems to have commonalities with the difference between 'Bristol Fairy' and 'Million Star' in G. paniculata. We analyzed the G. paniculata homologs of FKF1 (Hori et al, 2011). An E-box and TCTAG motif, which may be important in blue light-dependent FT expression (Liu et al, 2013;Shaikhali et al, 2012), were found in this region from MS.…”

Section: Discussionmentioning

confidence: 85%

“…7). The deleted region contained an E-box (CANNTG) and a TCTAG se- quence, which are reportedly associated with the response to blue light through the CRY pathway (Liu et al, 2013;Shaikhali et al, 2012).…”

mentioning

confidence: 99%

Characterization of Flowering-related Genes and Flowering Response in Relation to Blue Light in <i>Gypsophila paniculata</i>

et al. 2017

The flowering response to monochromatic light and flowering-related genes underlying this response need to be characterized to efficiently use light-emitting diodes for lighting culture. The flowering response to far-red light has been well studied in long-day cut flowers, but there have been few studies investigating the response to blue light. Flowering and the expression of the G. paniculata homologs of the FLOWERING LOCUS T and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 genes (GpFT, GpSOC1) were not previously promoted in Gypsophila paniculata, an important long-day cut flower, 'Bristol Fairy' under long-day conditions with blue light. In the present study, we found that flowering was promoted in another G. paniculata 'Million Star', under long-day conditions with blue light, suggesting that there is variation in G. paniculata's flowering response to blue light. Therefore, we analyzed the expression of GpFT and GpSOC1 in the 'Million Star'. The expression of GpFT and GpSOC1 was promoted with flowering in 'Million Star' under long-day conditions with blue light in contrast to 'Bristol Fairy'. We next analyzed the G. paniculata homologs (GpFKF1, GpGI) of FLAVIN-BINDING KELCH REPEAT F-BOX 1 and GIGANTEA genes, which participate in the flowering response to blue light. GpFKF1 and GpGI amino acid sequences were well conserved; gene expression showed a diurnal rhythm with different peaks under short-day and long-day conditions, as previously observed in Arabidopsis thaliana. GpFKF1 interacted with GpGI. There were no important differences in GpFKF1 or GpGI amino acid sequences between the two cultivars. Our results suggest that variation in the flowering response to blue light is associated with GpFT and GpSOC1, rather than GpFKF1 and GpGI.