Abstract
Although many transcription factors and regulatory proteins have been identified and functionally characterized in light signaling pathways, photoperception to transcription remains largely fragmented. The Z-box is one of the LREs (Light responsive elements) that plays important role in the regulation of transcription during light-controlled Arabidopsis seedling development. The involvement of photoreceptors in the modulation of the activity of the Z-box containing promoters has been demonstrated. However, the role of downstream signaling components such as SPA1 and MYC2/ZBF1, which are functionally interrelated, remains unknown. In this study, we have investigated the regulation of the Z-box containing synthetic and native promoters by SPA1 and MYC2 by using stable transgenic lines. Our studies suggest that SPA1 negatively regulates the expression of CAB1 native promoter. MYC2 negatively regulates the activity of Z- and/or G-box containing synthetic as well as native promoters irrespective of light quality. Moreover, MYC2 negatively regulates the expression of Z/G-NOS101-GUS even in the darkness. Furthermore, analyses of tissue specific expression in adult plants suggest that MYC2 strongly regulates the activity of Z- and G-box containing promoters specifically in leaves and stems. In roots, whereas MYC2 positively regulates the activity of the Z-box containing synthetic promoter, it does not seem to control the activity of the G-box containing promoters. Taken together, these results provide insights into SPA1- and MYC2-mediated transcriptional regulation of the Z- and G-box containing promoters in light signaling pathways.
Highlights
Light plays a pivotal role in the growth and development of plants starting from seed germination to de-etiolation of seedlings, pigment synthesis, chloroplast differentiation, flowering and senescence [1,2,3]
Seedlings undergo skotomorphogenesis, which is characterized by long hypocotyl, apical hook and development of proplastids into etioplasts, by contrast light grown seedlings show a characteristic pattern of development called photomorphogenesis, with short hypocotyl, open cotyledons, well developed chloroplasts and de-repression of light inducible genes [2,3,4]
SPA1 negatively regulates the accumulation of CAB1 in dark and blue light (BL) adapted seedlings [25]
Summary
Light plays a pivotal role in the growth and development of plants starting from seed germination to de-etiolation of seedlings, pigment synthesis, chloroplast differentiation, flowering and senescence [1,2,3]. Light modulates the gene expression primarily at the transcriptional level [4]. Photomorphogenesis is one of the well-studied photo-responses in Arabidopsis. Seedlings undergo skotomorphogenesis (etiolation), which is characterized by long hypocotyl, apical hook and development of proplastids into etioplasts, by contrast light grown seedlings show a characteristic pattern of development called photomorphogenesis (de-etiolation), with short hypocotyl, open cotyledons, well developed chloroplasts and de-repression of light inducible genes [2,3,4]. During the switch from skotomorphogenesis to photomorphogenesis, transcriptional reprogramming of a large number of genes occurs in Arabidopsis. Biochemical and mutational studies of Arabidopsis seedling development have identified several genes, which function downstream to phytochrome, cryptochrome or both the signaling pathways [2], [4],
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