Disease relevance of nifD

• The nitrogen fixation gene nifD was completely sequenced from representatives of these genera and analyzed phylogenetically, by using the representatives of other genera of the heterocystous cyanobacteria as outgroups [1].
• An 11-kilobase-pair element interrupts the nifD gene in vegetative cells of Anabaena sp. strain PCC 7120 [2].
• The xisA gene was shown to be the only Anabaena gene required for the proper rearrangement in E. coli of a plasmid containing the borders of the nifD element [2].
• Southern analysis of vegetative cell and heterocyst DNA from A. cylindrica and a Fox+ revertant of Nostoc Mac (isolate R2) showed rearrangement of the nifD and fdxN elements in heterocysts [3].

High impact information on nifD

• The DNA elements are named after the genes that they interrupt: nifD, fdxN, and hupL [4].
• In the NtcA-overproducing strain, heterocyst differentiation, induction of NtcA-dependent heterocyst development genes or operons such as devBCA or the cox2 operon, and NtcA-dependent excision of the 11-kb nifD-intervening element only took place under nitrogen deficiency [5].
• The ntcA mutant was unable to form heterocysts and did not rearrange the nifD or fdxN elements after induction on a medium lacking combined nitrogen [6].
• Similar inverted repeats are found within each of those three segments, and the sequences of these repeats bear some similarity to the 11-bp direct repeats flanking the 11-kb insertion interrupting the nifD gene of this strain (J. W. Golden, S. J. Robinson, and R. Haselkorn, Nature [London] 314:419-423, 1985) [7].
• RFLP analyses with Anabaena sp. strain PCC 7120 nifD excision element probes, including an xisA gene probe, detected homologous sequences in DNA extracted from the free-living isolates [8].

Chemical compound and disease context of nifD

• Alkane-induced expression, substrate binding profile, and immunolocalization of a cytochrome P450 encoded on the nifD excision element of Anabaena 7120 [9].

Biological context of nifD

• In developing heterocysts the nifD element excises from the chromosome via site-specific recombination between short repeat sequences that flank the element [10].
• Although the nifD 11-kb and nifS 55-kb rearrangements both occurred under normal aerobic heterocyst-inducing conditions, only the 55-kb excision occurred in argon-bubbled cultures, indicating that the two DNA rearrangements can be regulated differently [11].
• Some of the expression plasmids resulted in excision of the nifD element in a high proportion of vegetative cells [2].
• Four open reading frames with the same relative orientation as the nifD element-encoded xisA gene were identified in the sequenced region [10].
• Developmental rearrangement of cyanobacterial nif genes: nucleotide sequence, open reading frames, and cytochrome P-450 homology of the Anabaena sp. strain PCC 7120 nifD element [10].

Other interactions of nifD

• The Anabaena strain 7120 xisA gene is located at the nifK-proximal end of the nifD element and is required for excision of the element in heterocysts [12].
• Sequence analysis revealed regions of DNA that may form stem-loop structures in the intercistronic regions downstream of nifH and nifD [13].

References