Abstract
Submergence stress is a limiting factor for direct-seeded rice systems in rainfed lowlands and flood-prone areas of South and Southeast Asia. The present study demonstrated that submergence stress severely hampered the germination and seedling growth of rice, however, seed priming alleviated the detrimental effects of submergence stress. To elucidate the molecular basis of seed priming-induced submergence tolerance, transcriptome analyses were performed using 4-day-old primed (selenium-Se and salicylic acid-SA priming) and non-primed rice seedlings under submergence stress. Genomewide transcriptomic profiling identified 2371 and 2405 transcripts with Se- and SA-priming, respectively, that were differentially expressed in rice compared with non-priming treatment under submergence. Pathway and gene ontology term enrichment analyses revealed that genes involved in regulation of secondary metabolism, development, cell, transport, protein, and metal handling were over-represented after Se- or SA-priming. These coordinated factors might have enhanced the submergence tolerance and maintained the better germination and vigorous seedling growth of primed rice seedlings. It was also found that many genes involved in cellular and metabolic processes such as carbohydrate metabolism, cellular, and metabolic biosynthesis, nitrogen compound metabolic process, transcription, and response to oxidative stress were induced and overlapped in seed priming treatments, a finding which reveals the common mechanism of seed priming-induced submergence tolerance. Taken together, these results may provide new avenues for understanding and advancing priming-induced responses to submergence tolerance in crop plants.
Highlights
Direct seeding of rice is increasingly being adopted in both irrigated and rainfed areas because it reduces required energy and labor and improves resource use efficiency and system productivity (Liu et al, 2015)
All the growth attributes were significantly enhanced in Se+Sub and salicylic acid (SA)+Sub treatments compared with no priming + submergence stress (NP+Sub)
The seedling vigor index recorded in the Se+Sub and SA+Sub treatments was almost three times higher than that recorded in NP+Sub (Figure 1)
Summary
Direct seeding of rice is increasingly being adopted in both irrigated and rainfed areas because it reduces required energy and labor and improves resource use efficiency and system productivity (Liu et al, 2015). Rice is primarily planted by direct seeding in Australia, Europe, USA, Brazil, Chile, Cuba, and other Caribbean countries (Kaur et al, 2015). This method is becoming popular in many Asian countries. Kamolsukyunyong et al (2001) reported that approximately 15–20 million hectares of lowland rainfed rice cultivation area in South and Southeast Asia is prone to flooding. In irrigated areas, unleveled soil surfaces or heavy rainfall after seeding may result in submergence conditions. The uneven distribution of rainfall and extreme weather events in recent years due to climate change has increased the frequency and intensity of floods (Coumou and Rahmstorf, 2012)
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