isolation-characterization-intact-phycobilisome

Isolation and Characterization of Intact Phycobilisome in Cyanobacteria

In cyanobacteria, phycobilisome is a vital antenna protein complex that harvests light and transfers energy to photosystem I and II for photochemistry. ...

National Taiwan University

Glutathione S-transferases (GSTs) have been well documented to be involved in diverse aspects of biotic and abiotic stresses, especially detoxification processes. Whether they regulate plant development remains unclear. Here, we report on our isolation by reverse transcription-polymerase chain reaction of a plant GST, AtGSTU17, from Arabidopsis (Arabidopsis thaliana) and demonstrate that its expression is regulated by multiple photoreceptors, especially phytochrome A (phyA) under all light conditions. Further physiological studies indicated that AtGSTU17 participates in various aspects of seedling development, including hypocotyl elongation, anthocyanin accumulation, and far-red light-mediated inhibition of greening with a requirement of functional phyA. The loss-of-function mutant of AtGSTU17 (atgstu17) resulted in reduced biomass of seedlings and number of lateral roots in the presence of auxin, as well as insensitivity to abscisic acid (ABA)-mediated inhibition of root elongation, with similarity to different phyA mutant alleles. Moreover, the root phenotype conferred by atgstu17 was reflected by histochemical β-glucuronidase staining of AtGSTU17 promoter activity with the addition of auxin or ABA. Further microarray analysis of wild-type Columbia and atgstu17 seedlings treated with far-red irradiation or ABA revealed that AtGSTU17 might modulate hypocotyl elongation by positively regulating some light-signaling components and negatively regulating a group of auxin-responsive genes and modulate root development by negatively controlling an auxin transport protein in the presence of ABA. Therefore, our data reveal that AtGSTU17 participates in light signaling and might modulate various aspects of Arabidopsis development by affecting glutathione pools via a coordinated regulation with phyA and phytohormones.

A glutathione S-transferase regulated by light and hormones participates in the modulation of Arabidopsis seedling development.

Although glutathione S-transferases (GSTs) are thought to play major roles in oxidative stress metabolism, little is known about the regulatory functions of GSTs. We have reported that Arabidopsis (Arabidopsis thaliana) GLUTATHIONE S-TRANSFERASE U17 (AtGSTU17; At1g10370) participates in light signaling and might modulate various aspects of development by affecting glutathione (GSH) pools via a coordinated regulation with phytochrome A. Here, we provide further evidence to support a negative role of AtGSTU17 in drought and salt stress tolerance. When AtGSTU17 was mutated, plants were more tolerant to drought and salt stresses compared with wild-type plants. In addition, atgstu17 accumulated higher levels of GSH and abscisic acid (ABA) and exhibited hyposensitivity to ABA during seed germination, smaller stomatal apertures, a lower transpiration rate, better development of primary and lateral root systems, and longer vegetative growth. To explore how atgstu17 accumulated higher ABA content, we grew wild-type plants in the solution containing GSH and found that they accumulated ABA to a higher extent than plants grown in the absence of GSH, and they also exhibited the atgstu17 phenotypes. Wild-type plants treated with GSH also demonstrated more tolerance to drought and salt stresses. Furthermore, the effect of GSH on root patterning and drought tolerance was confirmed by growing the atgstu17 in solution containing l-buthionine-(S,R)-sulfoximine, a specific inhibitor of GSH biosynthesis. In conclusion, the atgstu17 phenotype can be explained by the combined effect of GSH and ABA. We propose a role of AtGSTU17 in adaptive responses to drought and salt stresses by functioning as a negative component of stress-mediated signal transduction pathways.

Drought and salt stress tolerance of an Arabidopsis glutathione S-transferase U17 knockout mutant are attributed to the combined effect of glutathione and abscisic acid.

To receive an ample amount of light, plants use elongation growth in response to vegetation shade. The combined interaction of light and hormones, including jasmonic acid (JA) signaling controls this elongation. However, the detailed molecular mechanisms underlying the response are still emerging. FAR-RED INSENSITIVE 219/JASMONATE RESISTANCE 1 (FIN219/JAR1), a cytoplasmic localized JA-conjugating enzyme, integrates far-red light and JA signaling. Here, we report that FIN219/JAR1 negatively regulates shade-induced hypocotyl elongation and gene expression in  seedlings in response to shade. In turn, simulated shade reduces FIN219 protein accumulation. Analysis of  double mutants indicated that FIN219 and phyA are synergistic in regulating shade-induced hypocotyl elongation and gene expression. Moreover, FIN219 differentially affected the expression of the shade-signaling bHLH factors PIF5 and PAR1, thereby increasing the expression of the auxin-response genes  and  on exposure to shade. Furthermore, the protein level of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) was affected in both  mutants and overexpression lines as compared with the wild type under shade. Intriguingly, ectopic expression of  inhibited the nuclear accumulation of COP1 in response to shade. Further co-immunoprecipitation studies revealed that FIN219 interacted with COP1 and phyA under shade. Therefore, FIN219/JAR1 may play a vital role in modulating the  response to simulated shade via multiple layers of molecular mechanisms.

Article	Year
A glutathione S-transferase regulated by light and hormones participates in the modulation of Arabidopsis seedling development. Plant physiology\| PubMed ID: 20935176	2010
Drought and salt stress tolerance of an Arabidopsis glutathione S-transferase U17 knockout mutant are attributed to the combined effect of glutathione and abscisic acid. Plant physiology\| PubMed ID: 22095046	2012
FAR-RED INSENSITIVE 219/JAR1 Contributes to Shade Avoidance Responses of Seedlings by Modulating Key Shade Signaling Components. Frontiers in plant science\| PubMed ID: 29163619	2017

Han-Wei Jiang

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