Poster: Nutrient Biology

Abs # 398: Expression of non-symbiotic hemoglobin genes in response to nitrate, nitrite, and nitric oxide in cultured rice cells

Presenter:	Ohwaki, Yoshinari , ohwaki@affrc.go.jp
Authors	Ohwaki, Yoshinari  (A)   Kawagishi-Kobayashi, Makiko  (B)   Wakasa, Kyo  (B)   Yoneyama, Tadakatsu  (C)   Fujihara, Shinsuke  (A)
Affiliations:	(A): National Agricultural Research Center (B): National Institute of Crop Science (C): University of Tokyo

Non-symbiotic hemoglobins (nsHbs) are ubiquitous in plants with two distinct classes of nsHb genes in dicots whereas monocots may have one class. Recent microarray work indicated that class 1 nsHb gene are inducible by nitrate in Arabidopsis, though the factors associated with induction of nsHbs by nitrate as well as its role in nitrate assimilation have not been examined in detail. In this paper, we examined the effects of various nitrogen compounds in induction of nsHb genes in cultured rice cells. Rice possesses two class 1 nsHb genes, ORYsaGLB1a and ORYsaGLB1b. RT-PCR analysis using gene specific primers showed that the transcription of ORYsaGLB1a and ORYsaGLB1b was induced in nitrate treated rice cells. Maximal induction of ORYsaGLB1a and ORYsaGLB1b mRNA occurred after 8 h of treatment with nitrate. In nitrite-supplied cells, the induction of ORYsaGLB1a and ORYsaGLB1b mRNA were more rapid than nitrate treated cells, where ORYsaGLB1a and ORYsaGLB1b were detected 0.5-1 h after the addition of nitrite and increased to a maximum at 4 h. The treatment of rice cells with S-Nitroso-N-acetyl-DL-penicillmine (SNAP) or sodium nitroprusside (SNP), a nitric oxide donor, also resulted in an accumulation of ORYsaGLB1a and ORYsaGLB1b mRNA. Treatment of SNAP induced the accumulation ORYsaGLB1a and ORYsaGLB1b mRNA within 0.5 h, and the amount reached a maximum by 4 h after treatment. Application of amino acids including Glu, Gln, Asp or Asn to the medium had no effects for induction of nsHb genes. The present experiments indicate that nitrate, nitrite or nitric oxide is an effective inducer for nsHbs in cultured rice cells.