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

Abstract

Waterlogging causes germination failure in pea (Pisum sativum L.). Three genotypes (BARI Motorshuti-3, Natore local-2 [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. Genotypes Kaspa and NL-2 displayed different mechanisms of tolerance. In Kaspa, an energy conserving strategy was indicated by a strong upregulation of tyrosine protein kinsase and down regulation of linoleate 9S-lipoxygenase 5, a fat metabolism gene. In contrast, a faster energy utilization strategy was suggested in NL-2 by the marked upregulation of a subtilase family protein and peroxisomal adenine nucleotide carrier 2, a fat metabolizing gene. Waterlogging susceptibility in germinating seeds of genotype BARI Motorshuti-3 was linked to upregulation of a kunitz-type trypsin/protease inhibitor that blocks protein metabolism and may lead to excessive lipid metabolism and the membrane leakage associated with waterlogging 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.

Eco-Physiological Traits Related to Recovery from Complete Submergence in the Model Legume Lotus japonicus

“…This trade-off between growing during submergence versus a sit-and-wait response until water recedes is likely a part of the growth strategies to cope with complete submergence already known as "escape" and" quiescence", respectively [3,4]. However, this is one of the first reports demonstrating this trade-off across genotypes for a legume species such as L. japonicus, as most studies are available for rice ( [28,29], but see [30] for pea genotypes). In this regard, it is possible to speculate that genotypes growing during submergence aim at emerging their leaves above the water using carbon reserves (i.e., starch).…”

“…Shoot to root dry mass ratio (S:R) of submerged plants as an estimator for the potential of transpiration/water uptake under drained conditions showed a negative relationship with RGR during the first week of recovery across genotypes for plants coming from a week of submergence. This means that genotypes with low S:R (e.g., RILs 18,30,189) consistently displayed higher RGR during the early recovery ( Figure 3a). Even though this negative relation between RGR and S:R persisted during the late recovery (2nd week after submergence), the fitting was weaker than during the early recovery (compare adjustment parameters in Figure 3a vs. Figure 3b).…”

“…Importantly, differences in S:R ratio among genotypes were constitutive and not related to plant size, as there was no significant relationships between plant dry mass and S:R (r 2 = 0.34; p = 0.23). Four out of 12 genotypes, RILs 6, 47, 80, and Gifu, increased the S:R in response to complete submergence, while the other three genotypes, RILs 18,30 and 189, decreased the S:R (Figure 1b). Interestingly, three out of the four genotypes that increased the S:R also showed positive RGR during submergence (RILs 6 and 47, and Gifu).…”

Legumes—The art and science of environmentally sustainable agriculture

“…Soil waterlogging poses a severe threat to the yields of major legume crops including pea, chickpea, and mung bean that are particularly susceptible to this stress. Zaman et al () evaluated the germination ability of three contrasting pea genotypes under different waterlogging duration and conducted RNA‐Seq and gene expression studies to identify differentially expressed genes and related stress tolerance mechanisms. In summary, the authors suggest two contrasting tolerance mechanisms related to pea germination under waterlogging stress.…”

“…The characterization of novel germination markers such as those identified by the application of histone deacetylase inhibitors in Medicago truncatula are thus of fundamental importance (Pagano et al, 2018). In addition, the integrity of the seed testa membrane was found to be important in the survival of seedlings exposed to the stress caused by waterlogging (Zaman, Malik, Erskine, & Kaur, 2018). Various regions are likely to experience an increase in flood events owing to changing climate patterns (Pedersen, Perata, & Voesenek, 2017).…”