Modulation of the endosomal pathway for optimized response to drought stress: from model to crop plants

The current climate situation potentiates the need for distinctive crops which have to be high yielding and resilient to abiotic and biotic stresses, particularly to drought stress. Responses to stresses are regulated and coordinated by phytohormones, whose transport and perception are commonly centered around plasma membrane (PM)-localized proteins. Localization and abundance of these are organized by endosomal trafficking, whereby the post-translational modification of PM proteins with the small protein ubiquitin is key in signaling their endocytosis and degradation. This review focuses on the endosomal degradation pathway in plants with a special focus on a protein family termed TARGET OF MYB1 (TOM1)-LIKE (TOLs), responsible for initiating sorting of ubiquitinated proteins destined for degradation. TOLs, albeit having apparent redundancies, play a role in very specific pathways where they may be relevant for fine-tuning of plant hormone signaling by means of tightly controlled protein turnover. Understanding the function of TOLs could give key insights into the mechanisms by which plants define the trade-off between stress tolerance and plant development when faced with challenging environments. Findings obtained in the model plant Arabidopsis thaliana provide a solid foundation for translational research aimed at breeding more tolerant crops.