REGULATION OF Fe DEFICIENCY RESPONSES IN WT PEA AND SOME OF ITS MUTANTS (BRZ AND DGL) - Pisum Sativum - page 10

Figure 2. Fe toxicity symptoms in leaves of the pea dgl mutant when grown in nutrient
solution with 10 µM Fe-EDDHA (left). For comparison, leaves of the wt cv „Sparkle‟
grown under the same conditions (right). Notice the necrotic spots in the dgl leaves. To
avoid this toxicity, both mutants, dgl and brz , should be cultivated in nutrient solution
with 2-3 µM Fe-EDDHA.
responses (see Regulation of Fe responses…). In both mutants, their enhanced
ferric reductase activity and their constitutive activation of the Fe acquisition
genes PsFRO1 and PsRIT1 are inhibited upon addition of ethylene inhibitors to
the medium (Figure 1;[19]). Moreover, the brz mutant exhibits a low root
nodulation ability [20], which is partly restored upon treatment with the
ethylene inhibitors AVG or Ag + [22]. The dgl mutant also exhibits a low root
nodulation ability [20]. Since ethylene inhibits root nodulation [63], it is
tempting to suggest that both mutants could have some alterations related to
ethylene metabolism or perception [19].
A DAPTATION OF P EA TO I RON C HLOROSIS
Iron deficiency has been reported for many plant species and geographical
regions. The most common problems occur in sensitive crops cultivated in arid
and semi-arid regions, where calcareous soils are abundant [7]. In these soils,
bicarbonate is one of the most important factors causing Fe chlorosis in dicot
plants while hypoxia can aggravate its negative effects [5]. Factors that increase
bicarbonate concentration and/or that cause hypoxia in soils, like high moisture
(due to flooding or excessive irrigation) and compaction, can induce Fe chlorosis