GAINS AND LOSSES OF FOREIGN MITOCHONDRIAL CHROMOSOMES IN A HOLOPARASITIC PLANT

GATICA-SORIA, LEONARDO M.; ROULET, MARIA EMILIA; CERIOTTI, LUIS FEDERICO; SANCHEZ-PUERTA, M. VIRGINIA

Mendoza

Congreso; LVIII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research; 2022

In plants, horizontal gene transfer (i.e. the movement of DNA between non-mating organisms) has been widely reported inmitochondrial genomes (mtDNAs). It is particularly frequent in parasitic plants due to the intimate connections they establish withtheir host plants. Lophophytum mirabile (Balanophoraceae) is a root holoparasite that lacks chlorophyll and depends completelyon their mimosoid (Fabaceae) hosts. About ~70% of the mtDNA of an individual of L. mirabile sampled in the Calilegua NationalPark, province of Jujuy (LmCal), consists of foreign transferred tracts from mimosoid hosts. This mtDNA (821,906 bp in length)assembles into 64 circular chromosomes, of which 24 harbor protein, rRNA, and tRNA coding genes while the other 40 arecompletely devoid of known coding regions. The evolutionary dynamics and perpetuation of the mitochondrial chromosomes in L.mirabile are unknown. The aim of this work is to compare the mtDNAs from different populations of L. mirabile to examine thepresence/absence of mitochondrial chromosomes and their phylogenetic origin. For this purpose, total DNA was extracted fromflowers of two individuals of L. mirabile growing in Santa Clara, province of Jujuy (LmSC) and in Bolivia (LmBol), respectively,and sequenced with DNBseq technology. De novo assembly of LmSC mtDNA was performed using SPAdes v.3.15.2 and finishedwith CONSED v.29 resulting in a mtDNA of 66 circular chromosomes and 811,073 bp in length. All chromosomes carrying genesin LmCal (24) are also present in LmSC with an identity of 99.22-99.99%. In contrast, there is extensive variation in thepresence/absence of non-coding chromosomes among the three L. mirabile populations. Of the 40 noncoding chromosomes ofLmCal, six are absent and five are partially present (30-60%) in the LmSC mtDNA. Similarly, of the 42 noncoding chromosomes of LmSC, six are absent and six are partially present in LmCal. Furthermore, a draft assembly of the LmBol mtDNA revealed thatfour of the 12 chromosomes variably absent or present in the mtDNAs of LmCal and LmSC are present in LmBol. Interestingly,more than 70% of the noncoding chromosomes that are not shared among populations of L. mirabile are mostly foreign. Therefore,these results suggest that noncoding chromosomes evolve under genetic drift and their presence is sporadic in the differentpopulations of L. mirabile as a result of gains and losses of foreign DNA.