Revisiting the Neurospora crassa mitochondrial genome

Abstract

The mitochondrial genome of Neurospora crassa has been less studied than its nuclear counterpart, yet it holds great potential for understanding the diversity and evolution of this important fungus. Here we describe a new mitochondrial DNA (mtDNA) complete sequence of a N. crassa wild type strain. The genome with 64 839 bp revealed 21 protein‐coding genes and several hypothetical open reading frames with no significant homology to any described gene. Five large repetitive regions were identified across the genome, including partial or complete genes. The largest repeated region holds a partial nd2 section that was also detected in Neurospora intermedia, suggesting a rearrangement that occurred before the N. crassa speciation. Interestingly, N. crassa has a palindrome adjacent to the partial nd2 repeated region possibly related to the genomic rearrangement, which is absent in N. intermedia. Finally, we compared the sequences of the three available N. crassa complete mtDNAs and found low levels of intraspecific variability. Most differences among strains were due to small indels in noncoding regions. The revisiting of the N. crassa mtDNA forms the basis for future studies on mitochondrial genome organization and variability.

New insights into the structure and dynamics of the TOM complex in mitochondria

“…In contrast with the bacterial ancestor, mitochondria must accommodate bidirectional protein transfer, both from the cytosol to the OMM, IMS, IMM or mitochondrial matrix, as well as protein transfer from the mitochondrial genome-encoded proteins to the IMM compartment. Whereas the mitochondrial genome encodes only a few proteins (8 in S. cerevisiae [ 24 ], 13 in humans [ 25 , 26 ] and 21 in N. crassa [ 27 ]), over 1000 proteins [ 28 , 29 ] are required for mitochondrial function, so most have to be imported from the cytosol. The TOM complex has been shown to play a central role in the recognition of most mitochondrial proteins which are nuclear-encoded [ 30 ] and serve as the main entry gate for proteins to be targeted to either the OMM, IMS, IMM or mitochondrial matrix [ 29 , 31–33 ].…”