Cordoba, E. | Search bioRxiv

bioRxiv2025

ATG8i Autophagy activation is mediated by cytosolic Ca2+ under osmotic stress in Arabidopsis thaliana

Autophagy is a highly conserved catabolic process in eukaryotic cells that enables the degradation and recycling of damaged or unnecessary cytoplasmic components. It plays essential roles in both development and responses to environmental stress. In this study, we investigated the regulation of autophagy in response to osmotic stress, focusing on the dynamics of the RFP-tagged ATG8i protein and the potential involvement of cytosolic calcium ion (Ca{superscript 2}) in this process. Our findings indicate that both osmotic stress and Ca{superscript 2} signaling modulate the accumulation of RFP-ATG8i-labeled autophagosomes in a plant organ-specific manner. Furthermore, the observed colocalization of RFP-ATG8i with the endoplasmic reticulum (ER) marker HDEL suggests a significant role for ATG8i in ER-phagy, highlighting its potential contribution to ER turnover under stress conditions.

plant biology↗

bioRxiv2021

Interplay between positive and negative regulation by B3-type transcription factors is critical for the accurate expression of the ABA INSENSITIVE 4 gene.

The ABA-INSENSITIVE 4 transcription factor is key for the regulation of diverse aspects of plant development and environmental responses, including proper perception of hormonal and nutritional signals. ABI4 activity is highly regulated at the transcriptional and post-transcriptional levels leading to precise expression mainly in the developing seed and early seedling development. Based on genetic and molecular approaches in the current study we provide new insights into the central mechanism underpinning the transcriptional regulation of ABI4 during both seed and vegetative development. We identified a complex interplay between the LEC2 and ABI3 transcriptional activators and the HSI/VAL repressors that is critical for proper ABI4 expression. Interestingly, the regulation by these proteins relies on the two RY cis-acting motifs present two kb upstream of the ABI4 gene. Our analysis also shows that the chromatin landscape of the ABI4 loci is highly dependent on the LEC2 and HSI2/VAL proteins. LEC2 regulation extends to the vegetative development and the absence of this factor results in ABA- and sugar-insensitive signaling in the developing plant. This regulatory circuit functions as a major control module for the correct spatial-temporal expression of ABI4 and prevents its ectopic accumulation that is harmful to the plant.

developmental biology↗