YUCCA auxin biosynthetic genes are required for Arabidopsis shade avoidance.

Patricia Müller-Moulé,Stacey L. Harmer,Michael F. Covington,Christine M. Palmer,Kazunari Nozue,Melissa L. Pytlak,Andreah D. Wallace,Julin N. Maloof

doi:10.7717/peerj.2574

Patricia Müller-Moulé, Stacey L. Harmer + Show 6 more

Open Access

https://doi.org/10.7717/peerj.2574

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Journal: PeerJ	Publication Date: Oct 13, 2016
Citations: 69	License type: CC BY 4.0

Affiliation: Department of Plant Biology, Castleton University

Abstract

Plants respond to neighbor shade by increasing stem and petiole elongation. Shade, sensed by phytochrome photoreceptors, causes stabilization of PHYTOCHROME INTERACTING FACTOR proteins and subsequent induction of YUCCA auxin biosynthetic genes. To investigate the role of YUCCA genes in phytochrome-mediated elongation, we examined auxin signaling kinetics after an end-of-day far-red (EOD-FR) light treatment, and found that an auxin responsive reporter is rapidly induced within 2 hours of far-red exposure. YUCCA2, 5, 8, and 9 are all induced with similar kinetics suggesting that they could act redundantly to control shade-mediated elongation. To test this hypothesis we constructed a yucca2, 5, 8, 9 quadruple mutant and found that the hypocotyl and petiole EOD-FR and shade avoidance responses are completely disrupted. This work shows that YUCCA auxin biosynthetic genes are essential for detectable shade avoidance and that YUCCA genes are important for petiole shade avoidance.

Highlights

Because plants are dependent on light for photosynthesis they have developed a complex system of photoreceptors and downstream responses enabling them to optimize growth to their light environment (Kami et al, 2010)
Once in the nucleus phytochrome binds to and triggers the degradation of a family of bHLH transcription factors known as PHYTOCHROME INTERACTING FACTORS (PIFs), thereby inhibiting elongation and other phenotypes associated with foliar shade or darkness (Ni et al, 1998; Park et al, 2004)
We found that the kinetics of the eDR5 reporter response to EOD-far-red light (FR) were similar to the kinetics of YUCCA2,5,8, and 9 upregulation, suggesting that these genes are the critical YUCCAs for response to end-of-day far-red (EOD-FR)

Summary

Introduction

Because plants are dependent on light for photosynthesis they have developed a complex system of photoreceptors and downstream responses enabling them to optimize growth to their light environment (Kami et al, 2010). One critical aspect of plant light responses is neighbor detection and shade avoidance (Casal, 2013; Gommers et al, 2013). Plants detect the presence of neighbors by changes in the light quality: since photosynthetic tissue absorbs more red light (R) than far-red light (FR), foliar shade uniquely lowers the R:FR ratio. Changes in the R:FR ratio are detected by phytochrome photoreceptors that exist in two photoconvertible forms, the red light absorbing form, Pr, and the far-red light absorbing form, Pfr. In high R:FR conditions, such as direct sunlight, type II phytochromes are converted from Pr to Pfr and translocated from the cytoplasm to the nucleus (Yamaguchi et al, 1999). Once in the nucleus phytochrome binds to and triggers the degradation of a family of bHLH transcription factors known as PHYTOCHROME INTERACTING FACTORS (PIFs), thereby inhibiting elongation and other phenotypes associated with foliar shade or darkness (Ni et al, 1998; Park et al, 2004)

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