Abstract
In plants, an elevation in ambient temperature induces adaptive morphological changes including elongated hypocotyls, which is predominantly regulated by a bHLH transcription factor, PIF4. Although PIF4 is expressed in all aerial tissues including the epidermis, mesophyll, and vascular bundle, its tissue-specific functions in thermomorphogenesis are not known. Here, we show that epidermis-specific expression of PIF4 induces constitutive long hypocotyls, while vasculature-specific expression of PIF4 has no effect on hypocotyl growth. RNA-Seq and qRT-PCR analyses reveal that auxin-responsive genes and growth-related genes are highly activated by epidermal, but not by vascular, PIF4. Additionally, inactivation of epidermal PIF4 or auxin signaling, and overexpression of epidermal phyB suppresses thermoresponsive growth, indicating that epidermal PIF4-auxin pathways are essential for the temperature responses. Further, we show that high temperatures increase both epidermal PIF4 transcription and the epidermal PIF4 DNA-binding ability. Taken together, our study demonstrates that the epidermis regulates thermoresponsive growth through the phyB-PIF4-auxin pathway.
Highlights
In plants, an elevation in ambient temperature induces adaptive morphological changes including elongated hypocotyls, which is predominantly regulated by a bHLH transcription factor, phytochrome interacting factor 4 (PIF4)
To ascertain whether PIF4 in the vasculature is involved in the regulation of various developmental processes including the hypocotyl growth, we generated transgenic plants expressing PIF4-YFP under the control of vascular-specific promoter SUCROSE TRANSPORTER 2 (SUC2) in a pif1;pif3;pif4;pif[5] quadruple mutant background
We generated transgenic plants expressing PIF4-YFP driven by MERISTEM LAYER1 (ML1) and CHLOROPHYLL A/B BINDING PROTEIN 3 (CAB3) promoter to examine the physiological functions of epidermal and mesophyll PIF4, respectively
Summary
An elevation in ambient temperature induces adaptive morphological changes including elongated hypocotyls, which is predominantly regulated by a bHLH transcription factor, PIF4. Thermomorphogenesis refers to the morphological changes that occur in plants in response to a rise in ambient temperature[1] It is characterized by elongated stems and hypocotyls, hyponastic leaf growth, and thinned leaves[1,2]. It was revealed that phyB functions as a thermosensor for thermomorphogenesis and, phyB may regulate PIF4 activity in response to changes in ambient temperature as well as light conditions[23,24]. In addition to the direct regulation of auxin biosynthetic gene expression, PIF4 regulates auxin signaling by directly increasing the activities of auxin response factors (ARFs), at least partly by enhancing ARF binding to the promoters of target genes[29,30]. Growth regulation by two other hormones, brassinosteroids (BR) and gibberellic acids (GA), is mediated by PIF4
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
