SQUINT Positively Regulates Resistance to the Pathogen Botrytis cinerea via miR156–SPL9 Module in Arabidopsis

Abstract

SQUINT (SQN) regulates plant maturation by promoting the activity of miR156, which functions primarily in the miR156–SQUAMOSA PROMOTER BINDING PROTEIN-LIKE9 (SPL9) module regulating plant growth and development. Here, we show that SQN acts in the jasmonic acid (JA) pathway, a major signaling pathway regulating plant responses to insect herbivory and pathogen infection. Arabidopsis thaliana sqn mutants showed elevated sensitivity to the necrotrophic fungus Botrytis cinerea compared with wild type. However, SQN is not involved in the early pattern-triggered immunity (PTI) response often triggered by fungal attack. Rather, SQN positively regulates the JA pathway, as sqn loss-of-function mutants treated with B. cinerea showed reduced JA accumulation, JA response and sensitivity to JA. Furthermore, the miR156–SPL9 module regulates plant resistance to B. cinerea: mir156 mutant and SPL9 overexpression plants displayed elevated sensitivity to B. cinerea. Moreover, constitutively expressing miR156a or reducing SPL9 expression in the sqn-1 mutant restored sensitivity of Arabidopsis to B. cinerea and JA responses. These results suggest that SQN positively modulate plant resistance to B. cinerea through the JA pathway, and the miR156–SPL9 module functions as a bridge between SQN and JA to mediate plant resistance to this pathogen.

Identification of miRNAs Involving Potato-Phytophthora infestans Interaction

“…Most of known miRNAs and their function were consistent with previous work, such as miR156, miR159, miR171, miR5300, and miR6027 which were involved in plant immunity [ 9 , 34 , 35 , 36 ]. Some miRNAs could regulate R genes in plants directly, the miR482 family (stu-miR482a/d/e-3p and stu-miR482) mainly regulates NBS-LRR genes in eudicots, functioning as an essential component in plant disease resistance [ 37 ]; miR6024-3p regulates NLR genes to facilitate the disease caused by the necrotrophic pathogen [ 38 ].…”

Distinct function of SPL genes in age-related resistance in Arabidopsis

“…Recent studies showed that the miR156-SPL pathway involved in plant immunity. Disrupting miR156 function in Arabidopsis by mutating SQUINT (SQN), an Arabidopsis orthologue of cyclophilin 40, compromised jasmonic acid signaling and disease resistance against necrotrophic pathogen Botrytis cinerea [ 26 ]. Furthermore, overexpressing miR156-targeted SPL9 in juvenile plants enhanced accumulation of reactive oxygen species and induced salicylic acid (SA) signaling, leading to enhanced resistance of Arabidopsis against bacterial pathogen Pseudomonas syringae [ 27 ].…”

Distinct function of SPL genes in age-related resistance inArabidopsis

“…Recent studies showed that the miR156-SPL pathway involved in plant immunity. Disrupting miR156 function in Arabidopsis by mutating SQUINT (SQN), an Arabidopsis orthologue of cyclophilin 40, compromised jasmonic acid signaling and disease resistance against necrotrophic pathogen Botrytis cinerea (27). Furthermore, overexpressing miR156-targeted SPL9 in juvenile plants enhanced accumulation of reactive oxygen species and induced salicylic acid (SA) signaling, leading to enhanced resistance of Arabidopsis against bacterial pathogen Pseudomonas syringae (28).…”