Arabidopsis FHY3 and FAR1 Regulate the Balance between Growth and Defense Responses under Shade Conditions

Abstract

Increasing crop yield per unit of area can be achieved by increasing planting density. However, high-density planting could trigger shade avoidance responses, which cause exaggerated growth and increased susceptibility to various diseases. Previous studies have shown that the rapid elongation of plants under shade (i.e., reduced red to far-red ratios) is regulated by phytochromes and various phytohormones. However, the detailed molecular mechanisms governing the interaction among these signaling pathways are not well understood. Here, we report that loss-of-function mutants of FAR-RED ELONGATED HYPOCOTYL3 (FHY3) and FAR-RED-IMPAIRED RESPONSE1 (FAR1), which encode two homologous transcription factors essential for phytochrome signaling, exhibit an exaggerated shade avoidance phenotype. We show that FHY3 and FAR1 repress plant growth through directly activating the expression of two atypical basic helix-loop-helix transcriptional cofactors, PHYTOCHROME RAPIDLY REGULATED1 (PAR1) and PAR2, and that this process is antagonized by a group of JASMONATE ZIM-DOMAIN proteins, key repressors of the jasmonic acid (JA) signaling pathway, through physical interactions. Furthermore, we show that FHY3 interacts with MYC2, a key transcriptional regulator of JA responses, coordinately regulating JA-responsive defense gene expression. Our results unveil a previously unrecognized mechanism whereby plants balance their growth and defense responses through convergence of the phytochrome signaling pathway and JA signaling pathway under shade conditions.

FHY3 and FAR1 Integrate Light Signals with the miR156-SPL Module-Mediated Aging Pathway to Regulate Arabidopsis Flowering

“…The mutant alleles fhy3-11 (N502711), far1-4 (N531652), and ful-7 (N797870) were purchased from the European Arabidopsis Stock Center. fhy3-11, far1-4, fhy3 far1, and overexpressors (FHY3-OE) have been described in Liu et al (2019). ful-7 has been described in Wang et al (2009).…”

Photosynthesis in a Changing Global Climate: Scaling Up and Scaling Down in Crops

“…In particular, during the last years, a selection of these models have been tested and compared to characterize their ability to simulate crop production at different sites across the globe situated in different continents and representing different climatic conditions for major crops such as wheat ( Asseng et al, 2013 ), maize ( Bassu et al, 2014 ), rice ( Li T. et al, 2015 ), and potato ( Fleisher et al, 2017 ). The aim was also to apply the models to estimate possible future impacts of a changing climate on global crop production and grain yields ( Asseng et al, 2019 ; Liu Y. et al, 2019 ).…”

Transcriptional regulatory network of the light signaling pathways

“…It was recently suggested that FHY3 and FAR inhibit the shade avoidance response by promoting the expression of PAR1 and PAR2, and the inhibition is counteracted by JAZ proteins. FHY3 also interacts with MYC2/3/4 to activate JA-responsive defense gene expression and the defense response, suggesting a role of FHY3/FAR1 in the balance between growth and defense (Liu et al, 2019). Thus, FHY3/FAR1 has emerged as a key player in light and hormone signal integration.…”