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Context: Salt stress harms plant growth and limits crop productivity. Autophagy is a material decomposition and metabolism pathway that is central to regulating plant responses to environmental stimuli and may be employed in plant breeding for stress tolerance. The autophagy-related gene ATG8 has become an essential tool for monitoring autophagic activity. Aims: We aimed to determine the effects of increased autophagic activity via overexpression of ATG8 on tolerance of wheat (Triticum aestivum L.) seedlings to NaCl stress. Methods: Salt-tolerant wheat cv. Jimai22 was used to produce TaATG8a -overexpressing wheat seedlings using Foxtail mosaic virus based virus-mediated overexpression technology. TaATG8a -overexpressing seedlings were exposed to NaCl stress for 6 days. Key results: Overexpression of TaATG8a enhanced autophagic activity and improved salt stress tolerance of wheat seedlings. Overexpression of TaATG8a also reduced damage to photosystem II, reduced excess accumulation of reactive oxygen species, increased the activities of superoxide dismutase, peroxidase and catalase, and suppressed programmed cell death in wheat seedling leaves during NaCl treatment. Conclusions: Overexpression of TaATG8a conferred higher tolerance of wheat seedlings to NaCl stress and suppressed salt-induced programmed cell death, accompanied by increased autophagic activity. Implications: This study provides genetic resources and a theoretical basis for stress tolerance breeding in wheat. The present study examined whether overexpression of TaATG8 enhanced tolerance of wheat seedlings to NaCl stress. TaATG8 -overexpressed seedlings showed higher autophagic activity, decreased ROS production, and improved activities of POD, SOD, and CAT under NaCl stress. TaATG8 -mediated autophagy inhibited programmed cell death in wheat leaves at the seedling stage during NaCl treatment. [ABSTRACT FROM AUTHOR]

As essential calcium ion (Ca2+) sensors in plants, calcium-dependent protein kinases (CDPKs) function in regulating the environmental adaptation of plants. However, the response mechanism of CDPKs to salt stress is not well understood. In the current study, the wheat salt-responsive gene TaCDPK27 was identified. The open reading frame (ORF) of TaCDPK27 was 1875 bp, coding 624 amino acids. The predicted molecular weight and isoelectric point were 68.905 kDa and 5.6, respectively. TaCDPK27 has the closest relationship with subgroup III members of the CDPK family of rice. Increased expression of TaCDPK27 in wheat seedling roots and leaves was triggered by 150 mM NaCl treatment. TaCDPK27 was mainly located in the cytoplasm. After NaCl treatment, some of this protein was transferred to the membrane. The inhibitory effect of TaCDPK27 silencing on the growth of wheat seedlings was slight. After exposure to 150 mM NaCl for 6 days, the NaCl stress tolerance of TaCDPK27-silenced wheat seedlings was reduced, with shorter lengths of both roots and leaves compared with those of the control seedlings. Moreover, silencing of TaCDPK27 further promoted the generation of reactive oxygen species (ROS); reduced the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT); aggravated the injury to photosystem II (PS II); and increased programmed cell death (PCD) in wheat leaves under NaCl treatment, confirming that the TaCDPK27-silenced seedlings exhibited more NaCl injury than control seedlings. Taken together, the decrease in NaCl tolerance in TaCDPK27-silenced seedlings was due to excessive ROS accumulation and subsequent aggravation of the NaCl-induced PCD. TaCDPK27 may be essential for positively regulating salt tolerance in wheat seedlings. [ABSTRACT FROM AUTHOR]

Metacaspases (MCAs), a family of caspase-like proteins, are important regulators of programmed cell death (PCD) in plant defense response. Autophagy is an important regulator of PCD. This study explored the underlying mechanism of the interaction among PCD, MCAs, and autophagy and their impact on wheat response to salt stress. In this study, the wheat salt-responsive gene TaMCA-Id was identified. The open reading frame (ORF) of TaMCA-Id was 1,071 bp, coding 356 amino acids. The predicted molecular weight and isoelectric point were 38,337.03 Da and 8.45, respectively. TaMCA-Id had classic characteristics of type I MCAs domains, a typical N-terminal pro-domain rich in proline. TaMCA-Id was mainly localized in the chloroplast and exhibited nucleocytoplasmictrafficking under NaCl treatment. Increased expression of TaMCA-Id in wheat seedling roots and leaves was triggered by 150 mM NaCl treatment. Silencing of TaMCA-Id enhanced sensitivity of wheat seedlings to NaCl stress. Under NaCl stress, TaMCA-Id -silenced seedlings exhibited a reduction in activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), higher accumulation of H2O2 and O 2. − , more serious injury to photosystem II (PSII), increase in PCD level, and autophagy activity in leaves of wheat seedlings. These results indicated that TaMCA-Id functioned in PCD through interacting with autophagy under NaCl stress, which could be used to improve the salt tolerance of crop plants. [ABSTRACT FROM AUTHOR]

Salt stress, as an abiotic stress, limits crops production worldwide. Autophagy and programmed cell death (PCD) have been functionally linked to plant adaptation to abiotic stress. However, the relation of autophagy and PCD is still under debate and the mechanism behind remains not fully understood. In this study, salt-tolerant wheat cultivar Jimai22 was used as the experimental material, and 150 mM NaCl was added to the hydroponic culture to test the effect of salt treatment. The results showed that NaCl stress enhances autophagic activity and induced occurrence of PCD in roots and leaves of wheat seedlings. Then, the barley stripe mosaic virus-induced silencing (BSMV-VIGS) method was used to inhibit autophagy by silencing the expression of ATG2 or ATG7. The results showed that silencing of ATG2 or ATG7 significantly inhibited autophagy and impaired the tolerance of wheat to NaCl stress. Moreover, silencing of ATG2 or ATG7 disrupted the absorption of Na, Cl, K and Ca elements and led to subsequent disequilibrium of Na+, Cl-, K+ and Ca2+, induced generation of excess reactive oxygen species (ROS), decreased the antioxidant activity, damaged photosynthesis apparatus, increased the level of PCD and led to differential expression of the genes, two metacaspase genes, cysteine-rich receptor-like kinase (CRK) 10 , and CRK26 in leaves of wheat seedlings under NaCl stress. The effect of the inhibitor 3-methyladenine (3-MA) on roots and leaves of wheat seedlings was in accordance with that of ATG2 and ATG7 silencing. Our results suggest that autophagy negatively regulates salt-induced PCD, or limits the scale of salt-induced PCD to avoid severe tissue death in wheat seedlings. [Display omitted] • NaCl stress induced the occurrence of autophagy and PCD in wheat. • Inhibition of Autophagy impairs the tolerance of wheat to NaCl stress. • Autophagy negatively regulates of NaCl-induced PCD in wheat seedlings. [ABSTRACT FROM AUTHOR]