Abscisic acid inhibits germination of mature Arabidopsis seeds by limiting the availability of energy and nutrients

Abstract

The addition of abscisic acid (ABA) to mature non-dormant seeds inhibits their germination. This effect of ABA might be related to its natural function as an endogenous inhibitor of precocious germination during seed formation. In this work, we studied how ABA affects the germination of mature seeds and the growth of nascent seedlings of Arabidopsis thaliana (L.) Heynh. Our findings were as follows: (i) inhibition by ABA was gradual, dose-dependent, and did not disappear after germination; (ii) inhibition of germination was relieved by the addition of metabolizable sugars or amino acids to the plating media; (iii) the effect of sugars and amino acids was cooperative, indicating that these two groups of metabolites relieve different deficiencies; (iv) ABA caused appreciable alterations in energy and nitrogen metabolism; and (v) ABA prevented the degradation of the seed storage proteins. In summary, ABA appears to inhibit seed germination by restricting the availability of energy and metabolites. This mechanism seems consistent with other known effects of ABA.

Glucose delays seed germination in Arabidopsis thaliana

“…The finding that even low concentrations (1%) of glucose are able to delay seed germination (Fig. 1a) was unexpected, since low concentrations of metabolizable sugars are effective in relieving the inhibitory action of ABA and mannose during germination (Garciarrubio et al 1997;Pego et al 1999;Finkelstein and Lynch 2000). As expected, elevated levels of glucose (up to 5%) restricted germination more severely.…”

“…A similar effect of glucose was found for ABA-mediated inhibition of Arabidopsis seed germination. Application of metabolizable sugars relieved the inhibitory effect of ABA on germination but not on seedling growth (Garciarrubio et al 1997;Finkelstein and Lynch 2000). The glucose relief of ABA action was already effective at a concentration of 35 mM and the effect was enhanced by light (Finkelstein and Lynch 2000).…”

“…Most of these screens revealed a central role for the plant hormones abscisic acid (ABA; Arenas-Huertero et al 2000;Huijser et al 2000;Laby et al 2000;Rook et al 2001) and ethylene (Zhou et al 1998;Gibson et al 2001) in sugar-induced signalling during early seedling development (for review, see Gazzarrini and McCourt 2001;Rolland et al 2002). Many other processes are affected by sugars as well, including germination (Garciarrubio et al 1997;Pego et al 1999;Finkelstein and Lynch 2000).…”

The Arabidopsis Mitochondria-Localized Pentatricopeptide Repeat Protein PGN Functions in Defense against Necrotrophic Fungi and Abiotic Stress Tolerance

“…The independent restoration of growth responses with either ACC or NF also serves to further strengthen an ABA-dependent mechanism. Interestingly, low levels of Glc also have an inhibitory effect on germination, yet the effect is lessened in ABA-sensitive and -insensitive mutants (Garciarrubio et al, 1997;Price et al, 2003). Thus, the enhanced growth of pgn on media lacking Glc lends further support to its increased sensitivity to ABA (Fig.…”

Abscisic Acid Biosynthesis and Response

“…Consequently, although as little as 3 µM exogenous ABA is sufficient to suppress germination of mature seeds, it is not clear whether the low level of endogenous ABA remaining in Arabidopsis seeds at this stage regulates germination. Surprisingly, radicle emergence is observed even in the presence of up to 100 µM ABA when supplemented with low concentrations of sugar (either glucose or sucrose at 30-90 mM) or peptone, but greening and subsequent seedling growth is still blocked (Garciarrubio et al, 1997;Finkelstein and Lynch, 2000b). Although the exogenous sugar might permit germination by overcoming a nutritional deficiency resulting from inhibition of reserve mobilization by exogenous ABA (Garciarrubio et al, 1997), reserve mobilization via the glyoxylate cycle is not essential for germination, and post-germinative growth can be supported by either photosynthesis or exogenous sugar in the absence of a functional glyoxylate cycle (Eastmond et al, 2000).…”