Changes in gene expression during germination reveal pea genotypes with either 'quiescence' or 'escape' mechanisms of waterlogging tolerance



Waterlogging causes germination failure in pea (Pisum sativum L.). Three genotypes (BM-3, NL-2 and Kaspa) contrasting in ability to germinate in waterlogged soil were exposed to different durations of waterlogging. Whole genome RNAseq was employed to capture differentially expressing genes. The ability to germinate in waterlogged soil was associated with testa colour and testa membrane integrity as confirmed by electrical conductivity measurements. Among the most differentially regulated genes, upregulated gene tyrosine protein kinase responsible for metabolic regulation and downregulated LOX5 involved in fat metabolism indicated energy preservation in tolerant Kaspa, while in the other tolerant NL-2 subtilase family protein and PNC2 involved in protein and fat metabolism respectively showed upregulated expression suggesting energy utilization during waterlogging. By contrast, in sensitive genotype BM-3 high upregulation was recorded for the kunitz-type trypsin/protease inhibitor whose role is blocking the activity of protein metabolism leading to excessive lipid metabolism causing membrane leakage and subsequent seed damage. Pathway analyses based on gene ontologies showed seed storage protein metabolism as upregulated in tolerant genotypes and downregulated in the sensitive genotype. Understanding the tolerance mechanism provides a platform to breed for adaptation to waterlogging stress at germination in pea.
Date made available28 May 2018

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