Abstract
Uroporphyrinogen III methyl transferase (UPM1) and Sirohydrochlorin ferrochelatase (SIRB) are the important genes involved in the biosynthesis of siroheme, the prosthetic group of nitrite reductases (NiR) and sulfite reductases (SiR) involved in nitrogen and sulfur assimilation. Both UPM1 and SIRB could be potential candidate genes targeted for sustainable agriculture especially in N-deficient soil. The phylogenetic analysis revealed that these genes are highly conserved among algae, bryophytes and vascular plants including dicots and monocots. The Arabidopsis proteins UPM1 and SIRB have close similarity with Camelina sativa followed by Brassica napus, Brassica rapa, and Brassica oleracea of the family brassicaceae. The tissue specific expression studies revealed that both the gene are expressed in stem, flower and silique and have highest expression in leaves where the protein content is quite high. The in silico promoter analysis revealed the presence of several light-responsive elements like GATA box, G box, I box, SORLIP2, SORLIP5, SORLREP3 and SORLREP4. Therefore, expression of both the genes was minimal in etiolated seedlings and was upregulated in light. Photo-regulation of transcript abundance of UPM1 and SIRB involved in the biosynthesis of siroheme the cofactor involved in 6 electron reduction of NO(2)(-) and SO(3)(2-) by NiR and SiR is crucial as the gene expression of latter two enzymes along with other N and S assimilatory enzymes are also modulated by light.