MdHB7‐like positively modulates apple salt tolerance by promoting autophagic activity and Na⁺ efflux

Abstract

SUMMARYSalt stress adversely affects the yield and quality of crops and limits their geographical distribution. Studying the functions and regulatory mechanisms of key genes in the salt stress response is important for breeding crops with enhanced stress resistance. Autophagy plays an important role in modulating the tolerance of plants to various types of abiotic stressors. However, the mechanisms underlying salt‐induced autophagy are largely unknown. Cation/Ca2+ exchanger proteins enhance apple salt tolerance by inhibiting Na+ accumulation but the mechanism underlying the response to salt stress remains unclear. Here, we show that the autophagy‐related gene MdATG18a modulated apple salt tolerance. Under salt stress, the autophagic activity, proline content, and antioxidant enzyme activities were higher and Na+ accumulation was lower in MdATG18a‐overexpressing transgenic plants than in control plants. The use of an autophagy inhibitor during the salt treatment demonstrated that the regulatory function of MdATG18a depended on autophagy. The yeast‐one‐hybrid assay revealed that the homeodomain‐leucine zipper (HD‐Zip) transcription factor MdHB7‐like directly bound to the MdATG18a promoter. Transcriptional regulation and genetic analyses showed that MdHB7‐like enhanced salt‐induced autophagic activity by promoting MdATG18a expression. The analysis of Na+ efflux rate in transgenic yeast indicated that MdCCX1 expression significantly promoted Na+ efflux. Promoter binding, transcriptional regulation, and genetic analyses showed that MdHB7‐like promoted Na+ efflux and apple salt tolerance by directly promoting MdCCX1 expression, which was independent of the autophagy pathway. Overall, our findings provide insight into the mechanism underlying MdHB7‐like‐mediated salt tolerance in apple through the MdHB7‐like‐MdATG18a and MdHB7‐like‐MdCCX1 modules. These results will aid future studies on the mechanisms underlying stress‐induced autophagy and the regulation of stress tolerance in plants.

Functional identification of the calcineurin B-like protein PavCBL4 in modulating salt tolerance in sweet cherry

“…For split-LUC assays, gene CDSs were cloned into pRI101-nLUC and pRI101-cLUC vectors, then expressed in Nicotiana benthamiana leaves using the Agrobacterium-mediated transient expression method (Mei et al, 2023;Yang et al, 2023a;Yang et al, 2023b). The LUC fluorescence signal was detected using a Lumazone Pylon 2048B imaging system (Roper Scientific, MA, USA).…”

“…The Open FluorCam FC 800-O assessed the maximal quantum efficiency of photosystem II (PSII; Fv/Fm). Na + content was determined as described previously (Yang et al, 2021a;Yang et al, 2023b).…”

Genome-Wide Identification of Catalase Gene Family and the Function of SmCAT4 in Eggplant Response to Salt Stress

“…Due to their sessile nature, plants must endure various kinds of stresses such as heat [1,2], cold [3][4][5], salt [6,7], drought [8], heavy metal [9], insect infestation [10,11], and pathogens [12,13]. Reactive oxygen species (ROS) including hydrogen peroxide (H 2 O 2 ), oxygen free radical or superoxide (O 2− ), hydrogen free radical (•OH), and nonradical singlet oxygen ( 1 O 2 ) act as signaling molecules that modulate plant homeostatic mechanism [14,15].…”