Abstract
ABSTRACTThis study elucidates the involvement of auxin with Zn-efficiency (ZE) in Zn-efficient rice var. Pokkali. Pokkali showed no significant decrease in morpho-physiological features, electrolyte leakage and total soluble proteins due to Zn deficiency as compared with Zn-sufficient seedlings. However, auxin inhibitor under Zn deficiency severely affected these characteristics, suggesting that ZE is associated with auxin signaling in rice. Results further revealed significant decreases in the expression of Zn transporter genes (OsIRT1, OsZIP4 and OsZIP1), OsDMAS1 (deoxymugeneic acid synthase) and phytochelatin in roots due to auxin inhibitor. It implies that auxin signaling may trigger Zn uptake, transport and chelation in rice seedlings to withstand Zn-deficiency. Further, significant reduction of major S-metabolites (cysteine, methionine, glutathione) and antioxidant enzymes (superoxide dismutase and glutathione reductase) along with increased H2O2 content, due to auxin inhibitor under Zn deficiency compared with controls. Taken together, these findings reveal that mechanisms associated with ZE in Pokkali are dependent on auxin signaling.
Highlights
Zn deficiency causes leaf bronzing, delayed maturity and yield loss in rice (Dobermann & Fairhurst 2000; Fageria et al 2002)
Pokkali seedlings grown without triiodobenzoic acid (TIBA) treatment under Zn deficiency showed no significant changes in root length, root dry weight, shoot height, shoot dry weight and total chlorophyll concentrations in comparison with the seedlings grown under Zn-sufficient conditions (Table 1 and Figure 1)
Supplementation of TIBA in Zn-sufficient seedlings ceased lateral root formation leading to significant reduction in root length and root dry weight but had no effect on shoot features compared with the seedlings grown in either Zn+ or Zn– conditions (Table 1)
Summary
Zn deficiency causes leaf bronzing, delayed maturity and yield loss in rice (Dobermann & Fairhurst 2000; Fageria et al 2002). High pH and precipitation lead to Zn deficiency in soil (Kabir et al 2014). Zn deficiency in crops causes malnutrition in children and birth problems in pregnant women (Prasad 2009; Graham et al 2012). Few plant species are able to withstand Zn deficiency, which is known as Zn-efficiency (ZE) by modulating biochemical and molecular mechanisms. Most of the mechanisms conferring Fe and Zn deficiency tolerance are common (Wissuwa et al 2006; Höller et al 2014). Zn homeostasis in plants is tightly regulated by Zn sensors and metal chelators involved in Zn acquisition and sequestration (Clemens 2001)
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