A Role of the FUZZY ONIONS LIKE Gene in Regulating Cell Death and Defense in Arabidopsis

Abstract

Programmed cell death (PCD) is critical for development and responses to environmental stimuli in many organisms. FUZZY ONIONS (FZO) proteins in yeast, flies, and mammals are known to affect mitochondrial fusion and function. Arabidopsis FZO-LIKE (FZL) was shown as a chloroplast protein that regulates chloroplast morphology and cell death. We cloned the FZL gene based on the lesion mimic phenotype conferred by an fzl mutation. Here we provide evidence to support that FZL has evolved new function different from its homologs from other organisms. We found that fzl mutants showed enhanced disease resistance to the bacterial pathogen Pseudomonas syringae and the oomycete pathogen Hyaloperonospora arabidopsidis. Besides altered chloroplast morphology and cell death, fzl showed the activation of reactive oxygen species (ROS) and autophagy pathways. FZL and the defense signaling molecule salicylic acid form a negative feedback loop in defense and cell death control. FZL did not complement the yeast strain lacking the FZO1 gene. Together these data suggest that the Arabidopsis FZL gene is a negative regulator of cell death and disease resistance, possibly through regulating ROS and autophagy pathways in the chloroplast.

Detecting early signs of heat and drought stress in Phoenix dactylifera (date palm)

“…The two significantly expressed heat stress transcription factors (PDACT_KE332562.1_G003770 and PDACT_KE332562.1_G003780) were putative orthologs of Arabidopsis heat stress transcription factor A-2 (HsfA2), known to regulate the expression of a number of heat shock proteins (HSPs) in Arabidopsis and to induce the expression of L-ascorbate peroxidase 2 (APX2), Inositol-3-phosphate synthase isozyme 2 (IPS2) and galactinol synthases 1 and 2 (GolS1) [ 34 ]. Additionally, two negative regulators of cell death, orthologs of Bax inhibitor-1 family protein and Fuzzy Onions Like [ 35 , 36 ], were highly expressed in all three conditions suggesting suppression of cell death, as well as one positive regulator, putative ortholog of Arabidopsis BAG6 chaperone regulator [ 37 ]. In Arabidopsis, BAG6 is a positive regulator of heat shock factors and cell death.…”

The dynamin-like protein Fzl promotes thylakoid fusion and resistance to light stress in Chlamydomonas reinhardtii

“…Previous studies performed in the plant model Arabidopsis thaliana demonstrated that the absence of Fzl is responsible for a slow growth phenotype associated with pale green or partly chlorotic leaves [20,22], enlarged chloroplasts containing morphologically altered thylakoids [20] as well as activation of autophagy and cell death pathways [22,23]. In addition, photosynthetic impairment was observed in pale green leaves [21].…”

“…The absence of Fzl induces a slow growth phenotype associated with the development of pale green leaves in the Columbia (Col-0) ecotype [20,21]. In the Landsberg erecta (L er ) background, the slow growth was conserved but the older leaves developed chlorotic areas instead of homogenous bleaching [22,23]. fzl cells display enlarged chloroplasts with morphologically altered thylakoids.…”

“…fzl cells display enlarged chloroplasts with morphologically altered thylakoids. In addition, an accumulation of stromal vesicles was detected in Col-0 [20] whereas autophagosomes were visualized in the cytoplasm of fzl-L er mutant cells [23]. This upregulation of autophagy was associated with increased hydrogen peroxide deposit in the cell-wall and with activation of cell death signaling pathways [22,23].…”

“…In addition, an accumulation of stromal vesicles was detected in Col-0 [20] whereas autophagosomes were visualized in the cytoplasm of fzl-L er mutant cells [23]. This upregulation of autophagy was associated with increased hydrogen peroxide deposit in the cell-wall and with activation of cell death signaling pathways [22,23]. The analysis of photosynthetic electron transport chain components from thylakoids of the fzl Col-0 background revealed reduced levels of chlorophyll and decreased accumulation of cytochrome b 6 f complex in older pale green leaves exclusively [21].…”