Physio-biochemical and molecular stress regulators and their crosstalk for low-temperature stress responses in fruit crops: A review

Comparative Physiological and Transcriptome Analyses of Tolerant and Susceptible Cultivars Reveal the Molecular Mechanism of Cold Tolerance in Anthurium andraeanum

Anthurium andraeanum is a tropical ornamental flower. The cost of Anthurium production is higher under low temperature (non-freezing) conditions; therefore, it is important to increase its cold tolerance. However, the molecular mechanisms underlying the response of Anthurium to cold stress remain elusive. In this study, comparative physiological and transcriptome sequencing analyses of two cultivars with contrasting cold tolerances were conducted to evaluate the cold stress response at the flowering stage. The activities of superoxide dismutase and peroxidase and the contents of proline, soluble sugar, and malondialdehyde increased under cold stress in the leaves of the cold tolerant cultivar Elegang (E) and cold susceptible cultivar Menghuang (MH), while the soluble protein content decreased in MH and increased in E. Using RNA sequencing, 24,695 differentially expressed genes (DEGs) were identified from comparisons between cultivars under the same conditions or between the treatment and control groups of a single cultivar, 9132 of which were common cold-responsive DEGs. Heat-shock proteins and pectinesterases were upregulated in E and downregulated in MH, indicating that these proteins are essential for Anthurium cold tolerance. Furthermore, four modules related to cold treatment were obtained by weighted gene co-expression network analysis. The expression of the top 20 hub genes in these modules was induced by cold stress in E or MH, suggesting they might be crucial contributors to cold tolerance. DEGs were significantly enriched in plant hormone signal transduction pathways, trehalose metabolism, and ribosomal proteins, suggesting these processes play important roles in Anthurium's cold stress response. This study provides a basis for elucidating the mechanism of cold tolerance in A. andraeanum and potential targets for molecular breeding.

Near-Zero Temperatures Arrest Movement of the Diaheliotropic Malva sylvestris

In the present study, the diaheliotropic leaf movement pattern of Malva sylvestris in relation to the impact of low temperature is presented. Seasonal measurements of movement characteristics along with important aspects of plant function, such as chlorophyll content, water potential, PSII photochemistry, and phenological parameters were performed on plants in their natural environment. During the study period, low winter temperatures and a 10-day freezing event gave insights into the plant's response to harsh environmental conditions and the effect of the latter on leaf movement profile. Plant growth was significantly inhibited during low-temperature periods (leaf shedding) and the photosynthetic performance was seriously depressed, as judged by in vivo chlorophyll a fluorescence. Additionally, the diaheliotropic leaf movement pattern was arrested. Temperature rise in March triggered new leaf burst and expansion, enhancement of the photosynthetic performance, and the recovery of the diaheliotropic movement. The daily and seasonal profiles of the water potential were synergistically shaped by leaf movement and climatic conditions. We conclude that diaheliotropism of M. sylvestris is a dynamic process that coordinates with the prevailing temperatures in ecosystems like the studied one, reaching a full arrest under near-zero temperatures to protect the photosynthetic apparatus from over-excitation and prevent photoinhibition.

Sensing, signalling, and regulatory mechanism of cold-stress tolerance in plants

Cold stress is a crucial environmental factor influencing growth and distribution and possessing yield penalties. To survive in the cold, plants have evolved to use a range of molecular mechanisms. The major regulatory pathway under low-temperature stress involves the conversion of external stimulus into an internal signal that triggers a defence mechanism through a transcriptional cascade to counter stress. Cold-receptive mechanism and cell signalling involve cold-related signalling molecules, sensors, calcium signals, MAPK cascade, and ICE-COR-CBF pathway that modulate signal transduction in plants. Of these, the ICE-CBF-COR signalling is considered to be an important regulator for cold-stress acclimation. ICE stimulates acclimation to cold and plays a pivotal role in regulating CBF-mediated cold-tolerance mechanism. Thus, CBFs regulate COR gene expression by binding to its promoter. Similarly, the C-repeat binding factor-dependent signalling cascade also stimulates osmotic stress-regulatory gene expression. This review elucidates the regulatory mechanism underlying cold stress, i.e., signal molecules, cold receptors, signal-transduction pathways, metabolic regulation under cold stress, and crosstalk of regulatory pathways with other abiotic stresses in plants. The results may pave the way for crop improvement in low-temperature environments.

Responses of sorghum to cold stress: A review focused on molecular breeding

Climate change has led to the search for strategies to acclimatize plants to various abiotic stressors to ensure the production and quality of crops of commercial interest. Sorghum is the fifth most important cereal crop, providing several uses including human food, animal feed, bioenergy, or industrial applications. The crop has an excellent adaptation potential to different types of abiotic stresses, such as drought, high salinity, and high temperatures. However, it is susceptible to low temperatures compared with other monocotyledonous species. Here, we have reviewed and discussed some of the research results and advances that focused on the physiological, metabolic, and molecular mechanisms that determine sorghum cold tolerance to improve our understanding of the nature of such trait. Questions and opportunities for a comprehensive approach to clarify sorghum cold tolerance or susceptibility are also discussed.