Musa balbisiana genome reveals subgenome evolution and functional divergence

Banana cultivars (Musa ssp.) are diploid, triploid and tetraploid hybrids derived from Musa acuminata and Musa balbisiana. We presented a high-quality draft genome assembly of M. balbisiana with 430 Mb (87%) assembled into 11 chromosomes. We identified that the recent divergence of M. acuminata (A-genome) and M. balbisiana (B-genome) occurred after lineage-specific whole-genome duplication, and that the B-genome may be more sensitive to the fractionation process compared to the A-genome. Homoeologous exchanges occurred frequently between A- and B-subgenomes in allopolyploids. Genomic variation within progenitors resulted in functional divergence of subgenomes. Global homoeologue expression dominance occurred between subgenomes of the allotriploid. Gene families related to ethylene biosynthesis and starch metabolism exhibited significant expansion at the pathway level and wide homoeologue expression dominance in the B-subgenome of the allotriploid. The independent origin of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) homoeologue gene pairs and tandem duplication-driven expansion of ACO genes in the B-subgenome contributed to rapid and major ethylene production post-harvest in allotriploid banana fruits. The findings of this study provide greater context for understanding fruit biology, and aid the development of tools for breeding optimal banana cultivars

From diagnostic tools to decision: how to secure germplasm exchanges when plants harbor infective banana streak virus sequences in their genome

Numerous plants harbor viral sequences of known viruses in their genome albeit the integration in the host genome is not required in the life cycle of plant viruses. In banana, sequences of Banana streak virus (BSV) integrated within the B genome of banana plants as eBSV (endogenous BSV) spontaneously participate to plant infection by releasing a functional viral genome following stresses. The inability to identify such eBSV-risked plant has hampered the banana germplasm exchange and the use of the B genome in the breeding programs over the last 20 years. Besides, intensive cropping of banana containing risked eBSV such as plantain (cooking banana) represents a real threat of disease emergence not only for plantain but also for nearby plantations of dessert banana which is strongly susceptible to the disease. We elucidated the sequence and organization of eBSVs for three BSV species in the diploid M. balbisiana cultivar Pisang Klutuk Wulung (PKW), showing that eBSGFV and eBSOLV were di-allelic, with one infectious and one non-infectious allele, whereas that eBSIMV was monoallelic [1, 2]. Based on the sequences and the structure of these eBSV we developed several PCR and Derived Cleaved Amplified Polymorphic Sequences (dCAPS) markers and tested their robustness by genotyping each eBSV from numerous Musa samples covering a wide range of Musa diversity [3]. We used them to currently establish the eBSV ID of banana candidates (from the international Musa Germplasm Transit Center (ITC) (KU Leuven), EMBRAPA collection…) and their potential BSV phenotype. Our results and knowledge recently gained on eBSV allowed us to lift the international moratorium established in 2000 on the B genome movement, and its use in breeding programs. As part of the Musanet Conservation Thematic Group, which is composed of an international panel of scientific experts, we recently established a strategy (decision tree) for the safe distribution of eBSV-containing Musa germplam through Quarantines and indexing centers 4]. We also helped produce interspecific hybrids with disarmed eBSV [5] or without eBSV [6] and strongly involved in the modification of the French National rules authorizing now the introduction of risked natural plantain for their intensive cropping in Martinique and Guadeloupe

From diagnostic tools to decision: how to secure germplasm exchanges when plants harbor infective banana streak virus sequences in their genome

Numerous plants harbor viral sequences of known viruses in their genome albeit the integration in the host genome is not required in the life cycle of plant viruses. In banana, sequences of Banana streak virus (BSV) integrated within the B genome of banana plants as eBSV (endogenous BSV) spontaneously participate to plant infection by releasing a functional viral genome following stresses. The inability to identify such eBSV-risked plant has hampered the banana germplasm exchange and the use of the B genome in the breeding programs over the last 20 years. Besides, intensive cropping of banana containing risked eBSV such as plantain (cooking banana) represents a real threat of disease emergence not only for plantain but also for nearby plantations of dessert banana which is strongly susceptible to the disease. We elucidated the sequence and organization of eBSVs for three BSV species in the diploid M. balbisiana cultivar Pisang Klutuk Wulung (PKW), showing that eBSGFV and eBSOLV were di-allelic, with one infectious and one non-infectious allele, whereas that eBSIMV was monoallelic [1, 2]. Based on the sequences and the structure of these eBSV we developed several PCR and Derived Cleaved Amplified Polymorphic Sequences (dCAPS) markers and tested their robustness by genotyping each eBSV from numerous Musa samples covering a wide range of Musa diversity [3]. We used them to currently establish the eBSV ID of banana candidates (from the international Musa Germplasm Transit Center (ITC) (KU Leuven), EMBRAPA collection…) and their potential BSV phenotype. Our results and knowledge recently gained on eBSV allowed us to lift the international moratorium established in 2000 on the B genome movement, and its use in breeding programs. As part of the Musanet Conservation Thematic Group, which is composed of an international panel of scientific experts, we recently established a strategy (decision tree) for the safe distribution of eBSV-containing Musa germplam through Quarantines and indexing centers 4]. We also helped produce interspecific hybrids with disarmed eBSV [5] or without eBSV [6] and strongly involved in the modification of the French National rules authorizing now the introduction of risked natural plantain for their intensive cropping in Martinique and Guadeloupe

Mitochondrial membrane permeabilization during the apoptotic process.

Apoptosis may be viewed as a triphasic process. During the premitochondrial initiation phase, very different pro-apoptotic signal transduction or damage pathways can be activated. These pathways then converge on the mitochondrion, where they cause the permeabilization of the inner and/or outer membranes with consequent release of soluble intermembrane proteins into the cytosol. The process of mitochondrial membrane permeabilization would constitute the decision/effector phase of the apoptotic process. During the post-mitochondrial degradation phase downstream caspases and nucleases are activated and the cell acquires an apoptotic morphology. Recently, a number of different second messengers (calcium, ceramide derivatives, nitric oxide, reactive oxygen species) and pro-apoptotic proteins (Bax, Bak, Bid, and caspases) have been found to directly compromise the barrier function of mitochondrial membranes, when added to isolated mitochondria. The effects of several among these agents are mediated at least in part via the permeability transition pore complex (PTPC), a composite channel in which members of the Bcl-2 family interact with sessile transmembrane proteins such as the adenine nucleotide translocator. These findings suggest that the PTPC may constitute a pharmacological target for chemotherapy and cytoprotection

Low genetic diversity of Banana bunchy top virus, with a subregional pattern of variation, in Democratic Republic of Congo

Banana bunchy top virus (BBTV), belonging to the genus Babuvirus, is the most devastating and widespread banana virus. Banana and plantain are major crops in terms of household income and food security in Democratic Republic of Congo (DRC). Despite the large area under banana and plantain cultivation in the country, before this study, the genetic characterization of BBTV isolates had only been undertaken for two provinces. In the study presented here, genetic variation in BBTV was assessed from 52 BBTV isolates collected in five out of 11 provinces in DRC (Bandundu, Bas-Congo, Katanga, Kinshasa and Kasaï Oriental) and in two provinces using sequences previously described in databases. Full genome sequencing of DNA-R components was performed, revealing low genetic variation (98–100 % nucleotide identity) among the BBTV isolates detected. The phylogenetic analyses showed that all the DRC isolates were clustered in the South Pacific clade of BBTV. Based on the coding region for the replication initiator protein, haplotype diversity was estimated to be 0.944 ± 0.013, with 30 haplotypes from 68 isolates in DRC. Such diversity shows a haplotype distribution mainly at the sub-regional level in DRC. In addition, the sequence determination from the whole genome of selected isolates confirmed low genetic variation among isolates from seven DRC provinces (97–100 % nucleotide identity). This study strengthened the hypothesis of a single BBTV introduction some time ago, followed by the spread of the virus in the country

Current status of occurrence, genetic diversity and epidemiology of Banana (Musa spp.) viruses in Democratic Republic of Congo

Viruses are major constraints to the production and exchange of banana and plantain (Musa spp.) germplasm in the world. Several viruses are recognized to affect Musa spp: Banana bunchy top virus (BBTV), Banana streak GF virus (BSGFV), Banana streak OL virus (BSOLV), Banana streak IM virus (BSIMV), Banana streak MY virus (BSMYV), Cucumber mosaic virus (CMV), Banana bract mosaic virus, (BBrMV). To date, in Democratic Republic of Congo (DRC), except BBTV, others banana viruses are not yet reported. The main aim of this work was to elucidate the epidemiological situation, genetic variability and origin of Musa spp. viruses in DRC

Current status of occurrence, genetic diversity and epidemiology of Banana (Musa spp.) viruses in Democratic Republic of Congo

Viruses are major constraints to the production and exchange of banana and plantain (Musa spp.) germplasm in the world. Several viruses are recognized to affect Musa spp: Banana bunchy top virus (BBTV), Banana streak GF virus (BSGFV), Banana streak OL virus (BSOLV), Banana streak IM virus (BSIMV), Banana streak MY virus (BSMYV), Cucumber mosaic virus (CMV), Banana bract mosaic virus, (BBrMV). To date, in Democratic Republic of Congo (DRC), except BBTV, others banana viruses are not yet reported. The main aim of this work was to elucidate the epidemiological situation, genetic variability and origin of Musa spp. viruses in DRC

Molecular characterization of Banana bunchy top virus reveals widespread low genetic variation among isolates in Democratic Republic of Congo

Banana bunchy top virus (BBTV), is the most devastating and widespread banana virus. Banana and plantain (Musa spp.) are major crops in terms of household income and food security in Democratic republic of Congo (DRC) (1). Despite the large territory under banana and plantain cultivation in the country, the genetic characterization of BBTV isolates has been undertaken for two provinces. The main objectives of this work were to understand the genetic variability of DRC BBTV isolates and to determine their origin