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. 2015 Nov 18;6:1023. doi: 10.3389/fpls.2015.01023

FIGURE 1.

FIGURE 1

A hypothesized model for nutrients signaling crosstalk with NO and ABA during seed germination. The figure highlights the action points of nitrate and glucose in NO and ABA signaling pathways controlling alleviation of seed dormancy and promotion of Arabidopsis seed germination. In the context of ABA-mediated inhibition of seedling establishment, NIA/NR- and AtNOA1-mediated pathways of NO biosynthesis function in an additive way. NO-deficient seedlings showed a higher basal and induced expression of ABA-responsive genes, conferring enhanced resistance to dehydration. In Arabidopsis, ABA 8′-hydroxylase encoded by CYP707A2 is implicated in NO-mediated ABA catabolism and seed dormancy break (Liu et al., 2009). In the seed endosperm, group VII ERFs act as NO sensors and regulate ABI5 (ABSCISIC ACID INSENSITIVE 5), highlighting as molecular players in NO-ABA crosstalk during seed germination (Gibbs et al., 2014). NO nitrosylates ABI5 as a regulator to control ABA hormone signaling through its degradation (Albertos et al., 2015). AtGLR1.1 is a component of the HXK1-independent ABA pathway and can be expressed in presence of a N source such as nitrate or amino acids (Glu or Gln), promoting seed germination (Kang and Turano, 2003; Kang et al., 2004). NR, nitrate reductase; NO, nitric oxide; ABA, abscisic acid; GAs, gibberellins; GA3ox1 and GA3ox2, Gibberellic acid oxidase1 and 2; CYP707A2, Cytochrome P450 ABA 8′-hydroxylase; GLR1.1, putative glutamate receptor 1.1; TF, transcription factor.