Exogenous paclobutrazol effectively mitigates salt stress in 'Duli' (Pyrus betulifolia) seedlings by reducing Na plus /K plus ratio, improving their osmotic substances, and activating the expression level of SOS and ABA pathway genes

Soil salinization is responsible for reductions in soil utilization by plants. Paclobutrazol (PAC) is an important plant growth regulator that is responsive to multiple biotic and abiotic stresses. In this study, we measured the impact of salt stress and PAC treatments on the growth, physiology, transcriptome, and related genes expression level of 'Duli' (Pyrus betulifolia). Our results show that NP treatment (200 mM NaCl + 10 mu M PAC) improves this plant's morphological characters, decreases its Na+ content and Na+/K+ ratio from 9.33 % to 22.48 % compared to the NT (200 mM NaCl), increases its antioxidant enzyme activity, and inhibits its active oxygen as well as malondialdehyde content, and enables it to accumulate osmotic adjustment substances (i.e., proline and soluble sugar). NP treatment slows down chlorophyll degradation and regulation of endogenous hormones to safeguard photosynthesis. Further, combining the RNA-seq and q-PCR results reveals that NP increases the expression of salt overly sensitive (SOS) genes (SOS1, SOS2, SOS3), ion transporter (PbANN1, PbAKT), ABA receptor PbPYLs, and transcription factors (PbNAC, PbWRKY). In conclusion, this study's findings demonstrates that exogenous PAC is effective at countering salt stress-induced damage to 'Duli' seedlings, which can be applied to improve 'Duli' salt tolerance in pear production.