PT  - JOURNAL ARTICLE
AU  - Acheampong, Atiako Kwame
AU  - Shanks, Carly
AU  - Chang, Chai-Yi
AU  - Schaller, G. Eric
AU  - Dagdas, Yasin
AU  - Kieber, Joseph J.
TI  - EXO70D isoforms mediate selective autophagic degradation of Type-A ARR proteins to regulate cytokinin sensitivity
AID  - 10.1101/2020.02.07.938712
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.02.07.938712
4099  - http://biorxiv.org/content/early/2020/02/07/2020.02.07.938712.short
4100  - http://biorxiv.org/content/early/2020/02/07/2020.02.07.938712.full
AB  - The phytohormone cytokinin influences many aspects of plant growth and development, several of which also involve the cellular process of autophagy, including leaf senescence, nutrient re-mobilization, and developmental transitions. The Arabidopsis type-A Response Regulators (type-A ARR) are negative regulators of cytokinin signaling that are transcriptionally induced in response to cytokinin. Here, we describe a mechanistic link between cytokinin signaling and autophagy, demonstrating that plants modulate cytokinin sensitivity through autophagic regulation of type-A ARR proteins. Type-A ARR proteins were degraded by autophagy in an AUTOPHAGY-RELATED (ATG)5-dependent manner. EXO70D family members interacted with Type-A ARR proteins, likely in a phosphorylation-dependent manner, and recruited them to autophagosomes via interaction with the core autophagy protein, ATG8. Consistently, loss-of-function exo70D1,2,3 mutants compromised targeting of type-A ARRs to autophagic vesicles, have elevated levels of type-A ARR proteins, and are hyposensitive to cytokinin. Disruption of both type-A ARRs and EXO70D1,2,3 compromised survival in carbon-deficient conditions, suggesting interaction between autophagy and cytokinin responsiveness in response to stress. These results indicate that the EXO70D proteins act as selective autophagy receptors to target type-A ARR cargos for autophagic degradation, demonstrating that cytokinin signaling can be modulated by selective autophagy.