title: Physiological Mechanisms Only Tell Half Story: Multiple Biological Processes are involved in Regulating Freezing Tolerance of Imbibed Lactuca sativa Seeds.
abstract: The physiological mechanisms by which imbibed seeds survive freezing temperatures in their natural environment have been categorized as freezing avoidance by supercooling and freezing tolerance by extracellular freeze-desiccation, but the biochemical and molecular mechanisms conferring seed freezing tolerance is unexplored. In this study, using imbibed Lactuca sativa seeds we show that fast cooled seeds (60 °C h-1) suffered significantly higher membrane damage at temperature between -20 °C and -10 °C than slow cooled (3 °Ch-1) seeds (P < 0.05), presumably explaining viability loss during fast cooling when temperature approaches -20 °C. Total soluble sugars increase in low temperature environment, but did not differ significantly between two cooling rates (P > 0.05). However, both SOD activity and accumulation of free proline were induced significantly after slow cooling to -20 °C compared with fast cooling. RNA-seq demonstrated that multiple pathways were differentially regulated between slow and fast cooling. Real-time verification of some differentially expressed genes (DEGs) revealed that fast cooling caused mRNA level changes of plant hormone and ubiquitionation pathways at higher sub-zero temperature, whilst slow cooling caused mRNA level change of those pathways at lower sub-zero ttemperatures. Thus, we conclude that imbibed seed tolerate low temperature not only by physiological mechanisms but also by biochemical and molecular changes.
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China.
authors.forename: Ganesh K
authors.initials: GK
authors.lastname: Jaganathan
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Han
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China.
authors.forename: Weijie
authors.initials: W
authors.lastname: Li
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China.
authors.forename: Danping
authors.initials: D
authors.lastname: Song
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Song
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China.
authors.forename: Mengqi
authors.initials: M
authors.lastname: Shen
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China.
authors.forename: Chenxue
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China.
authors.forename: Baolin
authors.initials: B
authors.lastname: Liu
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D005615:Freezing; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D018545:Lactuca / Q000502:physiology*; D012639:Seeds / Q000378:metabolism*