Expression of soybean plant hemoglobin gene family under abiotic stresses.

Many abiotic stresses induce the generation of nitric oxide (NO) in plant tissues, where it functions as a signal molecule in stress responses. Plants modulate NO by oxidizing it to NO with plant hemoglobin (GLB), because excess NO is toxic to cells. At least eight genes encoding GLB have been identified in soybean, in three clades: , , and . However, it is still unclear which genes are responsible for NO regulation under abiotic stress in soybean. We exposed soybean roots to flooding, salt, and two NO donors-sodium pentacyanonitrosylferrate (III) dihydrate (SNP) and -nitroso--acetyl-d,l-penicillamine (SNAP)-and analyzed expression of genes. , one of two genes of soybean, significantly responded to both SNP and SNAP, and its induction was almost completely repressed by a NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. responded to flooding but not to salt, suggesting that it is responsible for NO regulation under NO-inducing abiotic stresses such as flooding. , one of two genes of soybean, did not respond to NO donors at all but did respond to flooding, at a lower level than These results suggest that flooding induces not only NO but also unknown factor(s) that induce gene in soybean.