Major flowering time gene, FLOWERING LOCUS C , regulates seed germination in Arabidopsis thaliana

Abstract

FLOWERING LOCUS C (FLC) is a major regulator of flowering responses to seasonal environmental factors. Here, we document that FLC also regulates another major life-history transition-seed germination, and that natural variation at the FLC locus and in FLC expression is associated with natural variation in temperaturedependent germination. FLC-mediated germination acts through additional genes in the flowering pathway (FT, SOC1, and AP1) before involving the abscisic acid catabolic pathway (via CYP707A2) and gibberellins biosynthetic pathway (via GA20ox1) in seeds. Also, FLC regulation of germination is largely maternally controlled, with FLC peaking and FT, SOC1, and AP1 levels declining at late stages of seed maturation. High FLC expression during seed maturation is associated with altered expression of hormonal genes (CYP707A2 and GA20ox1) in germinating seeds, indicating that gene expression before the physiological independence of seeds can influence gene expression well after any physical connection between maternal plants and seeds exists. The major role of FLC in temperature-dependent germination documented here reveals a much broader adaptive significance of natural variation in FLC. Therefore, pleiotropy between these major life stages likely influences patterns of natural selection on this important gene, making FLC a promising case for examining how pleiotropy influences adaptive evolution.life history ͉ pleiotropy ͉ vernalization ͉ natural variation ͉ FRIGIDA

Arabidopsis thaliana life without phytochromes

“…None of the seeds obtained germinated in the absence of GA (at least 200 seeds were tested). These results underscore the advantages of having used the ft background, which was recently shown to improve germination (28). The ft mutation caused a delay in flowering time in the quintuple phytochrome mutant background (Fig.…”

“…Previous failure could be due to the fact that the seeds of the quintuple mutant do not germinate if GA is not added to the substrate. Here, we initially obtained the quintuple phytochrome mutant in the ft mutant background, which has recently been shown to improve germination (28).…”

Response to joint selection on germination and flowering phenology depends on the direction of selection

“…In particular, life history traits that comprise complex phenotypes such as phenology (Armbruster, Pélabon, Bolstad, & Hansen, 2014; Murren, 2012; Peiman & Robinson, 2017), may have both genetic and functional linkages. For example, in Arabidopsis thaliana , the FLOWERING LOCUS C (FLC) gene regulates flowering time and mediates germination time by affecting seed dormancy through a pleiotropic genetic correlation (Chiang et al., 2009). Simultaneously, in A. thaliana and many flowering plants, the sequential nature of expression of phenological traits results in functional linkage, as the timing of flowering affects traits later in development such as fruit maturation and seed dispersal (Donohue, 2009; Galloway & Burgess, 2009; Lacey & Pace, 1983; Lacey, Roach, Herr, Kincaid, & Perrott, 2003).…”

Genetic and physiological bases for phenological responses to current and predicted climates

“…For instance, our model of Arabidopsis phenology is at present silent about the factors that influence the timing of germination, even though recent studies have shown that certain genes in the flowering time network are also involved in seed dormancy and germination behaviour (Heschel et al 2008;Chiang et al 2009). Both maternal environmental factors such as temperature ) and genetic factors (Alonso-Blanco et al 2003;Holdsworth et al 2008;Chiang et al 2009) affect germination behaviour in this species. Despite such advances, we still know relatively little about the natural seasonal and climatic conditions that are permissive for germination (see also review in Donohue 2009).…”