Understanding the effects of maternal environment in controlling seed dormancy

BENECH-ARNOLD, ROBERTO; MARIA VERONICA RODRIGUEZ; BATLLA DIEGO; FARNOCCHIA, ROCIO BELEN FERNANDEZ

Advances in seed science and technology for more sustainable crop production

Burleigh Dodds

Año: 2022; p. 91 - 125

Variation in an individual’s phenotype may be determined not only by thegenotype and environment of that individual but also by maternal effects, thatis, the contribution of the maternal parent to the phenotype of its offspringbeyond the equal chromosomal contribution expected from each parent(Roach and Wulff, 1987). Maternal effects in plants can be classified into threedifferent categories: (i) cytoplasmic genetic, (ii) endosperm nuclear and (iii)maternal phenotypic (Roach and Wulff, 1987).BDS_Ch4_Seed_V1_CED_docbook_new_indd.indd 1 11-05-2022 11:05:542 Understanding the effects of maternal environment in controlling seed dormancy© Burleigh Dodds Science Publishing Limited, 2022. All rights reserved.Cytoplasmic genetic maternal effects result from the fact that, in eukaryotes,some plastids and mitochondria have DNA (i.e., some genes had beenretained in these organelles after endo-symbiosis, instead of being transferredto the nucleus) which is directly transferred from the maternal plant to theprogeny during ovule formation and development. This type of maternal effectcontributes to heritable variation in numerous traits in plants.Double fertilization in angiosperms derives in a 3N endosperm with twonuclei from the maternal and only one from the paternal parent. This meansmore doses of maternal than paternal genes which leads to the secondcategory of maternal effects: endosperm nuclear effects. Beyond the factthat the endosperm is the site of action of enzymes important for seedlinggrowth until autotrophy is achieved, the female gametophyte, which derivesalso in endosperm after double fertilization, is where maternal imprintingprocesses (i.e., a form of epigenetic regulation through which methylation andde-methylation of target DNA sequences are determined in the central cell ofthe female gametophyte) take place. Maternal imprinting occurs during pre- andpost-fertilization stages and affects methylation patterns and, in consequence,expression patterns of genes in the developing endosperm (Kohler et al., 2012).But in turn, endosperm imprinting regulates gene methylation and expressionin the embryo through the production of nt siRNA which are translocated to theembryo, thus influencing the phenotype (Kohler et al., 2012).Maternal phenotypic effects result from the environment and/or thegenotype of the mother plant (Roach and Wulff, 1987). The tissues surroundingthe endosperm and the embryo are maternal since they derive from theinteguments of the ovule (the testa) and from the wall of the ovary (the pericarp).Hence, the influence of maternal phenotypic effects on traits that affect seedbehavior may occur via structure (Karssen, 1970; Pourrat and Jacques, 1975;Ceccato et al., 2015; Penfield and MacGregor, 2017) or physiology (Kendallet al., 2011).Maternal effects have consequences at many levels. They are consideredimportant sources of error in selection studies because of their non-Mendeliannature which reduces the precision of genetic work. However, it is only recentlythat the adaptive significance of maternal effects has started to be recognized.It has become evident that many maternal effects have been shaped by theaction of natural selection to act as a mechanism for adaptive phenotypicresponse to environmental heterogeneity (Mousseau and Fox, 1998). But, inaddition, there is evidence that understanding and even quantifying maternaleffects can yield tools of decisive importance for phenotype prediction whichcan be used in agriculture.