Towards Better Understanding of Pea Seed Dormancy Using Laser Desorption/Ionization Mass Spectrometry

Abstract

Seed coats of six pea genotypes contrasting in dormancy were studied by laser desorption/ionization mass spectrometry (LDI-MS). Multivariate statistical analysis discriminated dormant and non-dormant seeds in mature dry state. Separation between dormant and non-dormant types was observed despite important markers of particular dormant genotypes differ from each other. Normalized signals of long-chain hydroxylated fatty acids (HLFA) in dormant JI64 genotype seed coats were significantly higher than in other genotypes. These compounds seem to be important markers likely influencing JI64 seed imbibition and germination. HLFA importance was supported by study of recombinant inbred lines (JI64xJI92) contrasting in dormancy but similar in other seed properties. Furthemore HLFA distribution in seed coat was studied by mass spectrometry imaging. HLFA contents in strophiole and hilum are significantly lower compared to other parts indicating their role in water uptake. Results from LDI-MS experiments are useful in understanding (physical) dormancy (first phases of germination) mechanism and properties related to food processing technologies (e.g., seed treatment by cooking).

The role of the testa during the establishment of physical dormancy in the pea seed

“…While dormancy in white clover has been associated with a more pronounced cuticle (Galussi and Moya, 2017), in the dormant pea entries it was not the cuticle that represented the major barrier to water entry. As noted by Cechová et al (2017), hydroxylated fatty acids are an important determining factor in the dormancy expressed by JI92 and JI64 seeds, which agrees with the present conclusion, based on anatomical and histochemical analyses, that waxy compounds are among the more important features that distinguish dormant from non-dormant pea seed. As yet it has not been possible to determine whether the hydroxylated fatty acids are located within the cuticle or whether they are associated with the subcuticular wax layer.…”

“…In effect, therefore, both the establishment and the breaking of testa impermeability are complex processes that depend on a number of mechanisms. Seeds can be softened by temperature-induced changes in the structure of the waxy components of the macrosclereid cell wall (Zeng et al, 2005), so it is of relevance that the testa of dormant pea seeds contains a number of unique hydroxylated fatty acids (Cechová et al, 2017). The testa of non-dormant seeds tends to be thinner, softer and more elastic (as a result of a higher content of pectin, lower contents of cellulose and tannin and less extensive cell wall deposition) than that of dormant ones (Miao et al, 2001;Hradilová et al, 2017).…”

“…The testa gradually becomes impermeable during the later stages of seed maturation (Gillikin and Graham, 1991); the biochemical basis of this hardening varies among families and species. Testa thickness is influential (Miao et al, 2001), but is not the sole basis of impermeability (de Souza and Marcos-Filho, 2001), which is also affected by the testa's composition (Smýkal et al, 2014;Cechová et al, 2017;Hradilová et al, 2017). Cell wall thickness in the outer integuments varies throughout seed development (Verdier et al, 2013), along with the accumulation of polyphenolic compounds; oxidation products of the latter are thought to contribute to impermeability in both barrel medic (Medicago truncatula) and pea (Pisum sativum) (Marbach and Mayer, 1974;Werker et al, 1979;Moïse et al, 2005), but also modifies permeability in Arabidopsis (Debeaujon et al, 2000).…”

Plant Metabolomics in the Global Scenario of Food Security: A Systems-Biology Approach for Sustainable Crop Production

“…In addition, analysis of the seed-coat composition of six pea ( Pisum spp.) genotypes possessing different propensity to dormancy/germination showed higher levels of hydroxylated long-chain fatty acids in dormant genotypes [ 8 ]. Similarly, symbiotic interactions represent another relevant issue.…”

Addendum: Cechová, M. et al. Towards Better Understanding of Pea Seed Dormancy Using Laser Desorption/Ionization Mass Spectrometry. Int. J. Mol. Sci. 2017, 18, 2196

“…It has been brought to our attention that one funding project of Ministry of Education, Youth and Sports of the Czech Republic (LO1417) was missing in the Acknowledgement section of our published paper [ 1 ], and therefore we would like to add it and report the Acknowledgements as follows:…”