Dehydrin MtCAS31 promotes autophagic degradation under drought stress

Abstract

Drought stress seriously affects crop yield, and the mechanism underlying plant resistance to drought stress via macroautophagy/autophagy is not clear. Here, we show that a dehydrin, Medicago truncatula MtCAS31 (cold acclimation-specific 31), a positive regulator of drought response, plays a key role in autophagic degradation. A GFP cleavage assay and treatment with an autophagy-specific inhibitor indicated that MtCAS31 participates in the autophagic degradation pathway and that overexpressing MtCAS31 promotes autophagy under drought stress. Furthermore, we discovered that MtCAS31 interacts with the autophagy-related protein ATG8a in the AIM-like motif YXXXI, supporting its function in autophagic degradation. In addition, we identified a cargo protein of MtCAS31, the aquaporin MtPIP2;7, by screening an M. truncatula cDNA library. We found that MtPIP2;7 functions as a negative regulator of drought response. Under drought stress, MtCAS31 facilitated the autophagic degradation of MtPIP2;7 and reduced root hydraulic conductivity, thus reducing water loss and improving drought tolerance. Taken together, our results reveal a novel function of dehydrins in promoting the autophagic degradation of proteins, which extends our knowledge of the function of dehydrins.

Genome-wide Identification and Expression Analysis of Autophagy-related Genes (ATGs) in Medicago Truncatula

“…However, overexpression of MdATG18a enhances tolerance to drought stress in apple trees [53]. A recent study reported that autophagy improves drought tolerance in M. truncatula through degradation of the aquaporin MtPIP2;7, which interacts with the cargo receptor MtCAS31 [54]. Consistent with previous studies, our results revealed that the promoter of many MtATG genes contained the drought-related MBS cis-element (Fig.…”

Characterization of Drought-Responsive Transcriptome During Seed Germination in Adzuki Bean (Vigna angularis L.) by PacBio SMRT and Illumina Sequencing

“…It can interact with the aquaporin MtPIP2;7 protein MtCAS31, which is a negative regulator of drought response. MtCAS31 promoted degradation of MtPIP2;7 in the autophagic pathway so that water loss was reduced and drought tolerance was improved under drought stress (Li et al, 2019). In this study, one TIP1-2-like gene (GeneID: 108338861) and one autophagy-related gene (GeneID: 108324651) were significantly up-regulated in drought tolerant variety under stress ( Table 1), suggesting that they play crucial roles in regulation seed germination to acclimatize to drought response.…”

Autophagy: An Intracellular Degradation Pathway Regulating Plant Survival and Stress Response

“…On the other hand, overexpression of ATG18a in apple results in higher autophagy activity and increased drought tolerance, indicating the key role for autophagy in responses to drought (Sun et al, 2018). Recently, Medicago truncatula dehydrin MtCAS31 (cold acclimation-specific 31) was found to interact with both ATG8a and a negative drought stress regulator MtPIP2;7 to improve drought tolerance by facilitating autophagic degradation of MtPIP2;7, demonstrating that MtCAS31 functions as a positive regulator of drought-induced autophagy (Li et al, 2019b). Consistent with this idea, the Arabidopsis atg2 and atg7 mutants contain more oxidized proteins and are hypersensitive to both salt and osmotic stresses (Luo et al, 2017).…”