Production of Reactive Oxygen Intermediates (O2  ˙−, H2O2, and ˙OH) by Maize Roots and Their Role in Wall Loosening and Elongation Growth

Abstract

Cell extension in the growing zone of plant roots typically takes place with a maximum local growth rate of 50% length increase per hour. The biochemical mechanism of this dramatic growth process is still poorly understood. Here we test the hypothesis that the wall-loosening reaction controlling root elongation is effected by the production of reactive oxygen intermediates, initiated by a NAD(P)H oxidase-catalyzed formation of superoxide radicals (O 2•2 ) at the plasma membrane and culminating in the generation of polysaccharide-cleaving hydroxyl radicals (• OH) by cell wall peroxidase. The following results were obtained using primary roots of maize (Zea mays) seedlings as experimental material. OH, and to respond to• OH by wall loosening, in passing through the growing zone. Moreover, inhibitor studies indicate that• OH formation is essential for normal root growth.

Specific Aquaporins Facilitate the Diffusion of Hydrogen Peroxide across Membranes

“…TIP1 is highly expressed in cells surrounding developing vascular tissues in maize roots (57). High levels of ROS including H 2 O 2 have been detected in the same tissues and have been implicated in cell wall loosening and elongation growth (58). TIP1;1 may have a function in the regulation of the level of H 2 O 2 during xylem formation, which is likely to have a strong impact on the development of the whole plant via impaired long distance transport.…”

Impacts of methyl jasmonate and phenyl acetic acid on biomass accumulation and antioxidant potential in adventitious roots of Ajuga bracteosa Wall ex Benth., a high valued endangered medicinal plant

“…The involvement of elicitors in root growth in the present study may be attributed to the production of reactive oxygen intermediates (ROIs) in response to elicitors treatment at low level. ROIs such as (-OH) are usually produced by NADPH Oxidase (NOX) in the plant cells, result in wall loosening, cell extension and thus elongation and growth of roots (Gapper and Dolan 2006;Liszkay et al 2004). However, higher amount of elicitor specifically Me-J strongly inhibits root growth and thus decrease biomass accumulation (Thanh et al 2005).…”

Stress Response Versus Stress Tolerance: A Transcriptome Analysis of Two Rice Lines Contrasting in Tolerance to Phosphorus Deficiency

“…Additional indirect evidence suggests a link between root-specific gene expression patterns and genotypic difference in root growth and/or root hair length. Maize root elongation was shown to be dependent on an additional wall-loosening mechanism mediated via ROI, a process initiated by the NAD(P)H oxidase-catalyzed formation of superoxide radicals (O 2 − ; Liszkay et al 2004). One such NAD(P)H-dependent oxidoreductase (Os10g02390) was the gene with the biggest fold change difference between NIL6-4 and Nipponbare (6.4-fold higher in NIL6-4 roots).…”

“…At this point, knowledge about the regulation of root elongation and root hair growth in graminaceous plants is incomplete with competing views attributing cell wall loosening to either XTH, expansins, or NAD(P)H-oxidoreductase-dependent ROI release (Liszkay et al 2004;Vissenberg et al 2005). That several genes associated with two of these processes were among the few genes with significantly higher expression in roots of NIL6-4 could therefore suggest that they are involved in the ability to maintain root growth and/or root hair elongation in Pdeficiency-tolerant NIL6-4.…”