Abstract
Water deficit is one of the major limiting factors for apple (Malus domestica) production on the Loess Plateau, a major apple cultivation area in China. The identification of genes related to the regulation of water use efficiency (WUE) is a crucial aspect of crop breeding programs. As a conserved degradation and recycling mechanism in eukaryotes, autophagy has been reported to participate in various stress responses. However, the relationship between autophagy and WUE regulation has not been explored. We have shown that a crucial autophagy protein in apple, MdATG8i, plays a role in improving salt tolerance. Here, we explored its biological function in response to long-term moderate drought stress. The results showed that MdATG8i-overexpressing (MdATG8i-OE) apple plants exhibited higher WUE than wild-type (WT) plants under long-term moderate drought conditions. Plant WUE can be increased by improving photosynthetic efficiency. Osmoregulation plays a critical role in plant stress resistance and adaptation. Under long-term drought conditions, the photosynthetic capacity and accumulation of sugar and amino acids were higher in MdATG8i-OE plants than in WT plants. The increased photosynthetic capacity in the OE plants could be attributed to their ability to maintain optimal stomatal aperture, organized chloroplasts, and strong antioxidant activity. MdATG8i overexpression also promoted autophagic activity, which was likely related to the changes described above. In summary, our results demonstrate that MdATG8i-OE apple lines exhibited higher WUE than WT under long-term moderate drought conditions because they maintained robust photosynthesis, effective osmotic adjustment processes, and strong autophagic activity.
Highlights
Drought stress is one of the most widespread environmental constraints and inhibits plant growth and production by affecting every aspect of the plant, especiallyJia et al Horticulture Research (2021)8:81 ratio of the amount of CO2 fixed by photosynthesis to the amount of water vapor lost to the atmosphere[6].Photosynthesis plays a crucial role in plant growth because it produces carbohydrates and oxygen[7,8]
To analyze the biological function of MdATG8i under long-term moderate drought stress, two previously obtained transgenic lines of MdATG8i-OE apple were used for further treatment[37]
We investigated the phenotypes of the WT plants and MdATG8i overexpression lines after 80 days of long-term drought treatment
Summary
Drought stress is one of the most widespread environmental constraints and inhibits plant growth and production by affecting every aspect of the plant, especiallyJia et al Horticulture Research (2021)8:81 ratio of the amount of CO2 fixed by photosynthesis to the amount of water vapor lost to the atmosphere[6].Photosynthesis plays a crucial role in plant growth because it produces carbohydrates and oxygen[7,8]. Drought stress is one of the most widespread environmental constraints and inhibits plant growth and production by affecting every aspect of the plant, especially. Greater photosynthetic capacity is one of the key factors involved in improving the WUE of crops without excessive yield penalties under long-term drought conditions. The plant traits that maintain photosynthesis increase plant growth and WUE10. Photosynthetic activity is sensitive to water deficits because they result in a rapid decrease in stomatal aperture and damage to the photosynthetic machinery[11]. Photosystem II (PSII) is vulnerable to damage under various stresses, which results in reductions in electron transport and ATP synthesis[12,13]. Pigment complexes and chloroplast structures can be destroyed by the excessive reactive oxygen species (ROS) generated under drought stress, resulting in diminished photosynthetic capacity[11]
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