An assessment of the biotechnological use of hemoglobin modulation in cereals

Abstract

Non-symbiotic hemoglobin (nsHb) genes are ubiquitous in plants, but their biological functions have mostly been studied in model plant species rather than in crops. nsHb influences cell signaling and metabolism by modulating the levels of nitric oxide (NO). Class 1 nsHb is upregulated under hypoxia and is involved in various biotic and abiotic stress responses. Ectopic overexpression of nsHb in Arabidopsis thaliana accelerates development, whilst targeted overexpression in seeds can increase seed yield. Such observations suggest that manipulating nsHb could be a valid biotechnological target. We studied the effects of overexpression of class 1 nsHb in the monocotyledonous crop plant barley (Hordeum vulgare cv. Golden Promise). nsHb was shown to be involved in NO metabolism in barley, as ectopic overexpression reduced the amount of NO released during hypoxia. Further, as in Arabidopsis, nsHb overexpression compromised basal resistance toward pathogens in barley. However, unlike Arabidopsis, nsHb ectopic overexpression delayed growth and development in barley, and seed specific overexpression reduced seed yield. Thus, nsHb overexpression in barley does not seem to be an efficient strategy for increasing yield in cereal crops. These findings highlight the necessity for using actual crop plants rather than laboratory model plants when assessing the effects of biotechnological approaches to crop improvement.

Overexpression of phytoglobin in barley alters both compatible and incompatible interactions with the mildew pathogen Blumeria graminis

“…The exact role of phytoglobin needs to be further determined. Previous studies have shown that overexpression of phytoglobin can influence plant development (Hebelstrup et al ., ) and as the results here indicate, it may also reduce plant stress during pathogen infections. Interestingly, the delayed senescence of GPHb1 plants seemed to promote pathogen growth as evaluated by a significantly higher level of fungal DNA compared to the GP plants at 14 dai.…”

“…Overexpression of phytoglobin in plants has a range of potential, for instance as a way to increase resistance to abiotic stress (Hebelstrup et al, 2014) and as a strategy to counteract air pollution by removing NO (Kuruthukulangarakoola et al, 2017). Modulation of phytoglobin expression can also be a strategy for studying aspects of host defence against B. graminis to gain a more general understanding of defence pathways.…”

“…Two barley genotypes were used for the experiments: wildtype GP plants and lines of GP expressing cDNA of the barley phytoglobin class 1 gene HvHb1 (GPHb1) described previously in Hebelstrup et al (2014). These plants overexpress HvHb1-1 cDNA by use of the ectopic maize ubiquitin-2 promoter.…”

Jasmonic acid is a downstream component in the modulation of somatic embryogenesis by Arabidopsis Class 2 phytoglobin

“…While representing a valid framework integrating Pgb signaling in plant embryogenesis, this model is most probably incomplete in terms of the number of intermediates transducing the PGB2 response. During post-embryonic growth, both NO and MYC2 operate at the interphase of a variety of transduction pathways often involving hormones, predominantly jasmonic acid (JA) ( Chen et al , 2011 ; Mur et al , 2013 ). While the link between MYC2 and JA signaling has been well established during plant–pathogen interactions and insect predation ( Lorenzo and Solano, 2005 ), the relationship between NO and JA is far from clear.…”

Signaling through reactive oxygen and nitrogen species is differentially modulated in sunflower seedling root and cotyledon in response to various nitric oxide donors and scavengers

“…23 Role of non-symbiotic hemoglobin has also been investigated in NO metabolism in barley. 24 Further, it has been shown that endogenous NO content is lowered in non-symbiotic hemoglobin overexpressing spinach plants as compared with the wild type plants. 25 Non-symbiotic hemoglobin C O 2 C _NO !…”