Nonsymbiotic hemoglobins in rice are synthesized during germination and in differentiating cell types

Abstract

Shearman, L.; Mathiesen, M.; Zhou, Y.J.; Arredondo-Peter, R.; Sarath, Gautam; and Klucas, R. V., "Nonsymbiotic hemoglobins in rice are synthesized during germination and in differentiating cell types" (2001 Abstract: Nonsymbiotic hemoglobins (ns-Hbs) previously have been found in monocots and dicots; however, very little is known about the tissue and cell type localization as well as the physiological function(s) of these oxygen-binding proteins. We report the immunodetection and immunolocalization of ns-Hbs in rice (Oryza sativa L.) by Western blotting and in situ confocal laser scanning techniques. Ns-Hbs were detected in soluble extracts of different tissues from the developing rice seedling by immunoblotting. Levels of ns-Hbs increased in the germinating seed for the fi rst six days following imbibition and remained relatively constant thereafter. In contrast, ns-Hb levels decreased during leaf maturation. Roots and mesocotyls contained detectable, but low levels of ns-Hbs. Split-seed experiments revealed that ns-Hbs are synthesized de novo during seed germination and are expressed in the absence of any signal originating from the embryo. Immunolocalization of ns-Hbs by con-focal microscopy indicated the presence of ns-Hbs primarily in differentiated and differentiating cell types of the developing seedling, such as the aleurone, scutellum, root cap cells, sclerenchyma, and tracheary elements. To our knowledge, this is the fi rst report of the specifi c cellular localization of these proteins during seedling development.

A single hemoglobin gene in Myrica gale retains both symbiotic and non-symbiotic specificity

“…Non-symbiotic hemoglobin expression has also been detected in germinating seeds of Oryza sativa after imbibition (Ross et al 2001). Hardly any hemoglobin expression is observed in dry barley seeds, but germination results in expression of hemoglobin peaking two to three days after imbibition.…”

Plant hemoglobins: What we know six decades after their discovery

“…However, analysis by confocal microscopy revealed that nsHbs are localized in the cytoplasm of differentiated and differentiating cell types of the developing rice seedling, such as the aleurone, scutellum, root cap cells, sclerenchyma, and tracheary elements. The immunolocalization of nsHbs in the vasculature of root, mesocotyl and leaf tissues, specifically in the xylem, suggests that nsHbs play roles in the metabolism accompanying the differentiation of the xylem (Ross et al, 2001).…”

The Role of Reactive Oxygen and Nitrogen Species in Bioenergetics, Metabolism, and Signaling During Seed Germination

“…The endogenous production of NO starts likely not immediately upon but rather shortly after seed imbibition and corresponds to the condition when the internal oxygen becomes depleted. NO production from germinating seeds, similarly to other hypoxic plant tissues, coincides with expression of class-1 nonsymbiotic plant hemoglobin, which appears within 2 h after imbibition and which function was shown to be related to NO scavenging (Taylor et al 1994;Nie and Hill 1997;Duff et al 1998;Hunt et al 2001;Ross et al 2001;). In the reaction, which involves class 1 hemoglobin and corresponding methemoglobin reductase, NO is metabolized in a NADH-dependent reaction which yields nitrate (NO 3 À ) , 2006a, b, reviewed in Gupta et al 2011.…”

“…Class 1 hemoglobin mRNA is absent from dry barley seeds, but becomes detectable within 2 h of imbibition and is detectable in embryo, aleurone, roots, and coleoptile (Andersson et al 1996;Duff et al 1998;Ross et al 2001;Guy et al 2002). In barley and rice, class 1 hemoglobin expression persists for 2-3 days postimbibition and is further enhanced by exposing these tissues to hypoxic (low oxygen) stress (Guy et al 2002).…”

“…Since the initial discovery of nonsymbiotic hemoglobins in the roots of non-nodulating plant species (Bogusz et al 1988) and seeds of monocot species (Taylor et al 1994), it has become evident that class 1 nonsymbiotic hemoglobin is involved in both monocot and dicot seed germination events (Taylor et al 1994;Nie and Hill 1997;Duff et al 1998;Hunt et al 2001;Ross et al 2001;Lira-Ruan et al 2001). Class 1 hemoglobin mRNA is absent from dry barley seeds, but becomes detectable within 2 h of imbibition and is detectable in embryo, aleurone, roots, and coleoptile (Andersson et al 1996;Duff et al 1998;Ross et al 2001;Guy et al 2002).…”