Abstract
Spring maize is usually subjected to low-temperature stress during seed germination, which retards seedling growth later even under a suitable temperature. However, the mechanism underlying maize seed germination under low-temperature stress impacting seedling growth is still ambiguous. In this study, we used one low-temperature sensitive maize (SM) and one low-temperature resistance maize (RM) to investigate the mechanism. The results showed that the SM line had higher malondialdehyde content and lower total antioxidant capacity (TAC) and germination percentage than the RM line under low-temperature stress, indicating the vulnerability of SM line to low-temperature stress. Further transcriptome analysis revealed that seed germination under low-temperature stress caused the down-regulation of photosynthesis-related gene ontology terms in two lines. Moreover, the SM line displayed down-regulation of ribosome and superoxide dismutase (SOD) related genes, whereas genes involved in SOD and vitamin B6 were up-regulated in the RM line. Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that photosynthesis and antioxidant metabolism-related pathways played essential roles in response to low-temperature stress during seed germination. The photosynthetic system displayed a higher degree of damage in the SM line. Both qRT-PCR and physiological characteristics experiments showed similar results with transcriptome data. Taken together, we propose a model for maize seed germination in response to low-temperature stress.
Highlights
Maize (Zea mays L.) originated in tropical and subtropical areas and is naturally sensitive to low-temperature stress, especially during seed germination
When maize seeds germinated at 13°C for 4 days, the percentage of seeds showing radicle protrusion in the resistance maize (RM) line was higher compared to the sensitive maize (SM) line (Figure 1A)
To investigate the effects of maize seed germination under low-temperature stress impacting seedling growth under normal temperature, we set a similar accumulated temperature between 25°C for days (NT) and low-temperature stress followed by normal temperature (LNT) treatment
Summary
Maize (Zea mays L.) originated in tropical and subtropical areas and is naturally sensitive to low-temperature stress, especially during seed germination. As spring maize, seed germination and seedling growth at an early stage are usually subjected to low-temperature stress. Seed Germination Under Low-Temperature Stress is affected due to the inability of plants to respond quickly to favorable environmental changes (Sowiński et al, 2005). The mechanism underlying maize seed germination under low-temperature stress impacting seedling growth is still ambiguous. Numerous studies have shown that cold stress at the seedling stage affects photosynthesis by reducing the activity of photosystem II (PSII; Savitch et al, 2011). The chloroplast ultrastructure of seedlings developed under low-temperature stress is disordered and cannot be repaired after experiencing favorable conditions (Grzybowski et al, 2019). The mechanism of low-temperature stress at the germination stage affecting photosynthesis remains unknown
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