Exogenous Putrescine Increases Heat Tolerance in Tomato Seedlings by Regulating Chlorophyll Metabolism and Enhancing Antioxidant Defense Efficiency

Mohammad Shah Jahan; Md Mahadi Hasan; Fahad S Alotaibi; Nadiyah M Alabdallah; Basmah M Alharbi; Khaled M A Ramadan; Eslam S A Bendary; Dikhnah Alshehri; Dilfuza Jabborova; Doha A Al-Balawi; Eldessoky S Dessoky; Mohamed F M Ibrahim; Shirong Guo

doi:10.3390/plants11081038

Exogenous Putrescine Increases Heat Tolerance in Tomato Seedlings by Regulating Chlorophyll Metabolism and Enhancing Antioxidant Defense Efficiency

Plants (Basel). 2022 Apr 11;11(8):1038. doi: 10.3390/plants11081038.

Authors

Affiliations

¹ College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China.
² Department of Horticulture, Faculty of Agriculture, Sher-e-Bangla Agricultural University, Dhaka 1207, Bangladesh.
³ State Key Laboratory of Grassland Agro-Ecosystems, College of Ecology, Lanzhou University, Lanzhou 730000, China.
⁴ King Abdulaziz City for Science and Technology, Riyadh 12354, Saudi Arabia.
⁵ Department of Biology, College of Science, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia.
⁶ Department of Biology, Faculty of Science, University of Tabuk, Tabuk 71491, Saudi Arabia.
⁷ Central Laboratories, Department of Chemistry, King Faisal University, Al-Ahsa 31982, Saudi Arabia.
⁸ Department of Agricultural Biochemistry, Faculty of Agriculture, Ain Shams University, Cairo 11241, Egypt.
⁹ Institute of Genetics and Plant Experimental Biology, Uzbekistan Academy of Sciences, Kibray 111208, Uzbekistan.
¹⁰ Department of Biology, College of Science, Taif University, Taif 21944, Saudi Arabia.
¹¹ Department of Agricultural Botany, Faculty of Agriculture, Ain Shams University, Cairo 11566, Egypt.

Abstract

Crops around the world are facing a diversity of environmental problems, of which high temperatures are proving to be the most serious threat to crops. Polyamine putrescine (Put) acts as a master growth regulator that contributes to optimal plant growth and development and increased stress tolerance. Here, the current study aimed to elucidate how Put functions in regulating chlorophyll (Chl) metabolism, oxidative stress, and antioxidant defense, as well as to characterize the expression of genes related to heat stress in tomato seedlings under such stress. The results revealed that Put treatment significantly attenuates heat-induced damage by promoting biomass production, increasing photosynthetic efficiency, and inhibiting excessive production of oxidative stress markers. Heat stress markedly decreased the Chl content in the tomato leaf and accelerated the leaf yellowing process. However, Put-treated tomato seedlings showed a higher Chl content, which could be associated with the functions of Put in elevating PBGD activity (Chl biosynthesis enzyme) and suppressing the activity of the Chl catabolic enzyme (Chlase and MDCase). Under high-temperature stress, the expression levels of the gene encoding factors involved in Chl biosynthesis and Chl catabolism were significantly down- and upregulated, respectively, and this trend was reversed in Put-treated heat-stressed seedlings. In addition, exogenous application of Put boosted the activity of antioxidant enzymes, along with the levels of expression of their encoding genes, only in plants that were heat stressed. Furthermore, the expression levels of heat-shock-related genes (HSP90, HSP70, and HsfA1) were elevated in Put-treated, high-temperature-stressed tomato seedlings. Taken together, our results indicate that Put treatment significantly increases the heat tolerance of tomato seedlings, by elevating Chl concentrations and suppressing Chl catabolic enzyme activity, modulating endogenous free PA content, increasing antioxidant defense efficiency, and upregulating the expression of heat-shock-related genes.

Keywords: chlorophyll degradation; oxidative stress; photosynthesis; polyamines; thermotolerance; tomato.