Robust room temperature perpendicular magnetic anisotropy and anomalous Hall effect of sputtered NiCo2O4film.

Inverse spinel ferrimagnetic NiCo2O4(NCO) exhibits volatile physical properties due to the complex ion/valence occupation, which complicates the study its intrinsic properties. In this work, robust room temperature perpendicular magnetic anisotropy (PMA) is distinctly observed in high-quality RF-sputtered NCO film down to 3 uc (2.4 nm), confirmed by the room temperature anomalous Hall effect. The NCO films show a good metallic conductivity with a dimensional driven metal-insulator transition. The scaling relation between anomalous Hall conductivity (σxy) and the longitudinal conductivity (σxx) reveals the dirty metal behavior in conjunction with the contribution of intrinsic Berry phase or disorder-enhanced electron correlation contribute to the anomalous Hall effect for thick films while the dirty scaling law dominates for the thin films. This work introduces an oxide candidate with robust room temperature PMA as well as massive production ability for the functional spintronic applications.

Tuning Bienenstock-Cooper-Munro learning rules in a two-terminal memristor for neuromorphic computing.

In memristors, the implementation of the Bienenstock-Cooper-Munro (BCM) learning rule plays a significant role in the modulation balance of artificial synapses and the reduction of energy consumption owing to their sliding frequency threshold. At present, the BCM learning rule is mostly achieved by adjusting gating voltage or channel current in field effect transistors. However, owing to the lack of the tunable degrees of freedom, the progress of two-terminal memristors is limited to simulating the BCM learning rule. In this study, by adjusting the series resistance, three types of BCM-like learning rules are found in a two-terminal BaTiO3 memristor. Specifically, the abnormal BCM learning rule with high-frequency depression and low-frequency potentiation is obtained for a small series resistance, the monotonous BCM learning rule with high-frequency potentiation and low-frequency depression is achieved for a large series resistance, and the type of BCM learning rule with the enhanced depression effect is obtained for a moderate series resistance. These three BCM learning rules are related to the non-monotonous conductance modulation caused by the migration of ionized oxygen vacancies and are proved by X-ray photoelectron spectroscopy. Moreover, spike rate-dependent plasticity (SRDP) and history-dependent plasticity are achieved. This study offers promising prospects for neuromorphic computing.

Identification and analysis of lignin biosynthesis genes related to fruit ripening and stress response in banana (Musa acuminata L. AAA group, cv. Cavendish).

Background: Lignin is a key component of the secondary cell wall of plants, providing mechanical support and facilitating water transport as well as having important impact effects in response to a variety of biological and abiotic stresses. Results: In this study, we identified 104 genes from ten enzyme gene families related to lignin biosynthesis in Musa acuminata genome and found the number of MaCOMT gene family was the largest, while MaC3Hs had only two members. MaPALs retained the original members, and the number of Ma4CLs in lignin biosynthesis was significantly less than that of flavonoids. Segmental duplication existed in most gene families, except for MaC3Hs, and tandem duplication was the main way to expand the number of MaCOMTs. Moreover, the expression profiles of lignin biosynthesis genes during fruit development, postharvest ripening stages and under various abiotic and biological stresses were investigated using available RNA-sequencing data to obtain fruit ripening and stress response candidate genes. Finally, a co-expression network of lignin biosynthesis genes was constructed by weighted gene co-expression network analysis to elucidate the lignin biosynthesis genes that might participate in lignin biosynthesis in banana during development and in response to stresses. Conclusion: This study systematically identified the lignin biosynthesis genes in the Musa acuminata genome, providing important candidate genes for further functional analysis. The identification of the major genes involved in lignin biosynthesis in banana provides the basis for the development of strategies to improve new banana varieties tolerant to biological and abiotic stresses with high yield and high quality.

Artificial synapse based on 1,4-diphenylbutadiyne with femtojoule energy consumption.

Memristors as electronic artificial synapses have attracted increasing attention in neuromorphic computing. Especially, organic small molecule artificial synapses show great promise for low-energy neuromorphic devices. In this study, the basic functions of biological synapses including paired-pulse facilitation/paired-pulse depression (PPF/PPD), spike rate-dependent plasticity (SRDP) and fast Bienenstock-Cooper-Munro learning rules (BCM) have been successfully simulated in the 1,4-diphenylbutadiyne (DPDA) memristor device. Furthermore, ultra-low energy consumption (∼25 fJ per spike), linear and large conductance changes have been obtained in the small molecule DPDA device. This work makes a great contribution to improve the accuracy, speed and to reduce the energy consumption for neuromorphic computing.

Elucidating the role of MaBAM9b in starch degradation.

Banana is a typical starch conversion fruit. The high content of starch at harvest is quickly digested and converted to soluble sugars during the postharvest ripening process, ultimately contributing to fruit flavor. This process is regulated in a complex manner by genes and environmental factors. MaBAM9b is one of the main enzyme genes previously found by transcriptomic analysis to be highly expressed in banana fruit. However, its exact role in starch degradation remains unclear. Here, full-length MaBAM9b was isolated from banana fruit, and its subcellular localization, protein expression, and transient expression in banana fruit slices were investigated. In addition, sense and anti-sense MaBAM9b were transformed into rice (Oryza sativa L. japonica. cv. 'Nipponbare') to identify the function of MaBAM9b. MaBAM9b was 1599 bp and encoded 532 amino acids. It contained two conserved domains of PLN02803 and glycosyl hydrolase family 14 and was localized in the chloroplast. The protein expression pattern of MaBAM9b remained consistently high throughout banana fruit ripening and starch degradation. Transient overexpression or inhibition of MaBAM9b in banana fruit greatly improved or suppressed starch degradation. Genetic modification of rice indicated that overexpression of MaBAM9b greatly improved starch degradation and seed germination, while inhibition of its expression suppressed these biological processes. These results support the key role of MaBAM9b in starch degradation and provide a target gene for banana fruit quality improvement and biological breeding.

High-performance ferroelectric nonvolatile memory based on Gd-and Ni-codoped BiFeO3 films.

BiFeO3 (BFO), Bi0.92Gd0.08FeO3 (BGFO) and Bi0.92Gd0.08Fe0.95Ni0.05O3 (BGFNO) films are epitaxially grown on 0.7 wt% Nb-SrTiO3 (NSTO) substrates. The strong ferroelectric property in BGFNO film is confirmed by piezoresponse force microscopy (PFM) and polarization versus voltage (P-V) measurement. It is also found that the Au/BGFNO/NSTO devices possess a ferroelectric resistance switching (RS) effect. Gd- and Ni-codoped BiFeO3 is found to strongly enhance the resistance on/off ratio. A resistance on/off ratio as large as 3 × 106 is achieved with an applied pulse voltage of -8 V and +4 V. In addition, the devices exhibit excellent retention and anti-fatigue characteristics. The memristor behavior of Au/BGFNO/NSTO is attributed to the switching of polarization states, which modulate the width and height of the barrier at the BGFNO/NSTO interface. The excellent resistive switching properties in Au/BGFNO/NSTO devices indicate the promising application in nonvolatile memory.

Genome-Wide Analysis of the Banana WRKY Transcription Factor Gene Family Closely Related to Fruit Ripening and Stress.

WRKY transcription factors (TFs) play an important role in plant responses to biotic and abiotic stress as well as in plant growth and development. In the present study, bioinformatics methods were used to identify members of the WRKY transcription factor family in the Musa acuminata (DH-Pahang) genome (version 2). A total of 164 MaWRKYs were identified and phylogenetic analysis showed that MaWRKYs could be categorized into three subfamilies. Overall, the 162 MaWRKYs were distributed on 11 chromosomes, and 2 genes were not located on the chromosome. There were 31 collinear genes from segmental duplication and 7 pairs of genes from tandem duplication. RNA-sequencing was used to analyze the expression profiles of MaWRKYs in different fruit development, ripening stages, under various abiotic and biotic stressors. Most of the MaWRKYs showed a variety of expression patterns in the banana fruit development and ripening stages. Some MaWRKYs responded to abiotic stress, such as low temperature, drought, and salt stress. Most differentially expressed MaWRKYs were downregulated during banana's response to Foc TR4 infection, which plays an important role in physiological regulation to stress. Our findings indicate that MaWRKY21 directly binds to the W-box of the MaICS promoter to decrease MaICS transcription and then reduce the enzyme activity. These studies have improved our understanding of the molecular basis for the development and stress resistance of an important banana variety.

Genome-Wide Identification and Transcript Analysis of TCP Gene Family in Banana (Musa acuminata L.).

Plant-specific TEOSINTE-BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR1 (TCP) gene family has versatile functions in diverse aspects of plants. However, less research on banana TCPs was done comprehensively. Accordingly, 48 banana TCP genes were characterized on aspects of gene structure, conserved motifs, phylogenetic relationship, and expression patterns. Members of the MaTCP gene family were unevenly distributed among 11 chromosomes and purification selection was the driving force of the MaTCP gene family. Gene duplication analysis indicated that segmental duplication is the major contributor to family expansion. Promoter analysis showed that MaTCPs might be involved in banana growth, development, and abiotic stress responses. Further, the expression of 12 MaTCPs was analyzed by real-time quantitative RT-PCR, and the protein interaction analysis showed that MaPCF10 and MaPCF13 may have an important function in banana fruit development and ripening. These results lay the foundation for further study of the functions of TCP genes in banana.

Genome-Wide Characterization and Analysis of R2R3-MYB Genes Related to Fruit Ripening and Stress Response in Banana (Musa acuminata L. AAA Group, cv. 'Cavendish').

MYB is an important type of transcription factor in eukaryotes. It is widely involved in a variety of biological processes and plays a role in plant morphogenesis, growth and development, primary and secondary metabolite synthesis, and other life processes. In this study, bioinformatics methods were used to identify the R2R3-MYB transcription factor family members in the whole Musa acuminata (DH-Pahang) genome, one of the wild ancestors of banana. A total of 280 MaMYBs were obtained, and phylogenetic analysis indicated that these MaMYBs could be classified into 33 clades with MYBs from Arabidopsis thaliana. The amino acid sequences of the R2 and R3 Myb-DNA binding in all MaMYB protein sequences were quite conserved, especially Arg-12, Arg-13, Leu-23, and Leu-79. Distribution mapping results showed that 277 MaMYBs were localized on the 11 chromosomes in the Musa acuminata genome. The MaMYBs were distributed unevenly across the 11 chromosomes. More than 40.0% of the MaMYBs were located in collinear fragments, and segmental duplications likely played a key role in the expansion of the MaMYBs. Moreover, the expression profiles of MaMYBs in different fruit development and ripening stages and under various abiotic and biotic stresses were investigated using available RNA-sequencing data to obtain fruit development, ripening-specific, and stress-responsive candidate genes. Weighted gene co-expression network analysis (WGCNA) was used to analyze transcriptome data of banana from the above 11 samples. We found MaMYBs participating in important metabolic biosynthesis pathways in banana. Collectively, our results represent a comprehensive genome-wide study of the MaMYB gene family, which should be helpful in further detailed studies on MaMYBs functions related to fruit development, postharvest ripening, and the seedling response to stress in an important banana cultivar.

Overexpression of a Banana Aquaporin Gene MaPIP1;1 Enhances Tolerance to Multiple Abiotic Stresses in Transgenic Banana and Analysis of Its Interacting Transcription Factors.

Aquaporins can improve the ability of plants to resist abiotic stresses, but the mechanism is still not completely clear. In this research, overexpression of MaPIP1;1 in banana improved tolerance to multiple stresses. The transgenic plants resulted in lower ion leakage and malondialdehyde content, while the proline, chlorophyll, soluble sugar, and abscisic acid (ABA) contents were higher. In addition, under high salt and recovery conditions, the content of Na+ and K+ is higher, also under recovery conditions, the ratio of K+/Na+ is higher. Finally, under stress conditions, the expression levels of ABA biosynthesis and response genes in the transgenic lines are higher than those of the wild type. In previous studies, we proved that the MaMADS3 could bind to the promoter region of MaPIP1;1, thereby regulating the expression of MaPIP1;1 and affecting the drought tolerance of banana plants. However, the mechanism of MaPIP1;1 gene response to stress under different adversity conditions might be regulated differently. In this study, we proved that some transcription factor genes, including MaERF14, MaDREB1G, MaMYB1R1, MaERF1/39, MabZIP53, and MaMYB22, showed similar expression patterns with MaPIP1;1 under salt or cold stresses, and their encoded proteins could bind to the promoter region of MaPIP1;1. Here we proposed a novel MaPIP1;1-mediated mechanism that enhanced salt and cold tolerance in bananas. The results of this study have enriched the stress-resistant regulatory network of aquaporins genes and are of great significance for the development of molecular breeding strategies for stress-resistant fruit crops.

Transcription factor MaMADS36 plays a central role in regulating banana fruit ripening.

Bananas are model fruits for studying starch conversion and climactericity. Starch degradation and ripening are two important biological processes that occur concomitantly in banana fruit. Ethylene biosynthesis and postharvest fruit ripening processes, i.e. starch degradation, fruit softening, and sugar accumulation, are highly correlated and thus could be controlled by a common regulatory switch. However, this switch has not been identified. In this study, we transformed red banana (Musa acuminata L.) with sense and anti-sense constructs of the MaMADS36 transcription factor gene (also MuMADS1, Ma05_g18560.1). Analysis of these lines showed that MaMADS36 interacts with 74 other proteins to form a co-expression network and could act as an important switch to regulate ethylene biosynthesis, starch degradation, softening, and sugar accumulation. Among these target genes, musa acuminata beta-amylase 9b (MaBAM9b, Ma05_t07800.1), which encodes a starch degradation enzyme, was selected to further investigate the regulatory mechanism of MaMADS36. Our findings revealed that MaMADS36 directly binds to the CA/T(r)G box of the MaBAM9b promoter to increase MaBAM9b transcription and, in turn, enzyme activity and starch degradation during ripening. These results will further our understanding of the fine regulatory mechanisms of MADS-box transcription factors in regulating fruit ripening, which can be applied to breeding programs to improve fruit shelf-life.

Diamond anvil cell with double coaxial chambers.

In general, pressure calibration in diamond anvil cells (DACs) has been achieved by mixing pressure calibration materials (PCMs) with the sample inside the pressure chamber. However, the chemical reactions between the sample and PCMs are sometimes unavoidable at extreme conditions, such as high pressure and high temperature. These undesired reactions will cause pollution, induce changes in physical properties or phase transformations of PCMs, and result in tremendous error of pressure calibration. In this paper, we report a new design of DAC with double coaxial pressure chambers, sample and PCM chambers, to resolve the challenge by isolating the PCM from the sample. Our test results show that the pressure of the two chambers presents interesting relations with the anvil setup. When the geometric parameters of two anvil sets are the same and the difference of chamber diameters is within a certain range (i.e., below 10 µm), the pressure correlation between the two chambers shows little correlation with the pressure transmitting medium before and after its solidification at both room temperature and high temperatures within the experimental condition range (well below 20 GPa and 634 K). In this case, the pressure of the sample chamber can be well calibrated by the pressure of the PCM chamber. This new DAC setup is thus proved to be effective in calibrating the sample pressure below certain conditions while avoiding undesired sample pollution and pressure induced property changes in PCMs under high pressure and high temperature conditions compared with single-chamber DACs.

Characteristics of banana B genome MADS-box family demonstrate their roles in fruit development, ripening, and stress.

MADS-box genes are critical regulators of growth and development in flowering plants. Sequencing of the Musa balbisiana (B) genome has provided a platform for the systematic analysis of the MADS-box gene family in the important banana ancestor Musa balbisiana. Seventy-seven MADS-box genes, including 18 type I and 59 type II, were strictly identified from the banana (Pisang Klutuk Wulung, PKW, 2n = 2x = 22) B genome. These genes have been preferentially placed on the banana B genome. Evolutionary analysis suggested that M. balbisiana MCM1-AGAMOUS-DEFICIENS-SRF (MbMADS) might be organized into the MIKCc, MIKC*, Mα, Mß, and Mγ groups according to the phylogeny. MIKCc was then further categorized into 10 subfamilies according to conserved motif and gene structure analyses. The well-defined MADS-box genes highlight gene birth and death in banana. MbMADSes originated from the same ancestor as MaMADSes. Transcriptome analysis in cultivated banana (ABB) revealed that MbMADSes were conserved and differentially expressed in several organs, in various fruit developing and ripening stages, and in stress treatments, indicating the participation of these genes in fruit development, ripening, and stress responses. Of note, SEP/AGL2 and AG, as well as other several type II MADS-box genes, including the STMADS11 and TM3/SOC1 subfamilies, indicated elevated expression throughout banana fruit development, ripening, and stress treatments, indicating their new parts in controlling fruit development and ripening. According to the co-expression network analysis, MbMADS75 interacted with bZIP and seven other transcription factors to perform its function. This systematic analysis reveals fruit development, ripening, and stress candidate MbMADSes genes for additional functional studies in plants, improving our understanding of the transcriptional regulation of MbMADSes genes and providing a base for genetic modification of MADS-mediated fruit development, ripening, and stress.

Molecular identification of the key starch branching enzyme-encoding gene SBE2.3 and its interacting transcription factors in banana fruits.

Starch branching enzyme (SBE) has rarely been studied in common starchy banana fruits. For the first time, we report here the molecular characterization of seven SBE (MaSBE) and six SBE (MbSBE) genes in the banana A- and B-genomes, respectively, which could be classified into three distinct subfamilies according to genome-wide identification. Systematic transcriptomic analysis revealed that six MaSBEs and six MbSBEs were expressed in the developing banana fruits of two different genotypes, BaXi Jiao (BX, AAA) and Fen Jiao (FJ, AAB), among which MaSBE2.3 and MbSBE2.3 were highly expressed. Transient silencing of MaSBE2.3 expression in banana fruit discs led to a significant decrease in its transcription, which coincides with significant reductions in total starch and amylopectin contents compared to those of empty vector controls. The suggested functional role of MaSBE2.3 in banana fruit development was corroborated by its transient overexpression in banana fruit discs, which led to significant enhancements in total starch and amylopectin contents. A number of transcription factors, including three auxin response factors (ARF2/12/24) and two MYBs (MYB3/308), that interact with the MaSBE2.3 promoter were identified by yeast one-hybrid library assays. Among these ARFs and MYBs, MaARF2/MaMYB308 and MaARF12/MaARF24/MaMYB3 were demonstrated via a luciferase reporter system to upregulate and downregulate the expression of MaSBE2.3, respectively.

Genome-Wide Analysis of Basic Helix-Loop-Helix Transcription Factors to Elucidate Candidate Genes Related to Fruit Ripening and Stress in Banana (Musa acuminata L. AAA Group, cv. Cavendish).

The basic helix-loop-helix (bHLH) proteins are a superfamily of transcription factors (TFs) that can bind to specific DNA target sites, playing a central role in a wide range of metabolic, physiological, and developmental processes in higher organisms. However, no systemic analysis of bHLH TFs has been reported in banana, a typical climacteric fruit in tropical and subtropical regions. In our study, 259 MabHLH TF genes were identified in the genome of Musa acuminata (A genome), and phylogenetic analysis indicated that these MabHLHs could be classified into 23 subfamilies with the bHLHs from rice and Arabidopsis. The amino acid sequences of the bHLH domain in all MabHLH protein sequences were quite conserved, especially Arg-12, Arg-13, Leu-23, and Leu-79. Distribution mapping results showed that 258 MabHLHs were localized on the 11 chromosomes in the M. acuminata genome. The results indicated that 40.7% of gene duplication events were located in collinear fragments, and segmental duplications might have played a key role in the expansion of MabHLHs. Moreover, the expression profiles of MabHLHs in different fruit development and ripening stages and under various abiotic and biotic stresses were investigated using available RNA-sequencing data to obtain fruit development, ripening-specific, and stress-responsive candidate genes. Finally, a co-expression network of MabHLHs was constructed by weighted gene co-expression network analysis to elucidate the MabHLHs that might participate in important metabolic biosynthesis pathways in banana during development and the response to stress. A total of 259 MabHLHs were identified, and their sequence features, conserved domains, phylogenetic relationships, chromosomal distributions, gene duplications, expression profiles, and co-expression networks were investigated. This study systematically identified the MabHLHs in the M. acuminata genome at the genome-wide level, providing important candidate genes for further functional analysis. These findings improve our understanding of the molecular basis of developmental and stress tolerance in an important banana cultivar.

Genomic and Transcriptional Analysis of Banana Ovate Family Proteins Reveals Their Relationship with Fruit Development and Ripening.

Ovate Family Proteins (OFPs) belong to a plant-specific transcription factor family. They have been found to have significant roles in growth and development in Arabidopsis and tomato; however, little is known regarding their role in banana. Thus, a genome-wide study of OFP genes in banana was conducted for the first time in the present study. The results demonstrated that 49 OFP family members are unequally distributed across 11 chromosomes. Phylogenetic analysis grouped these genes into two subfamilies and eight subgroups, which was confirmed by the conserved motif and gene structure analysis. Furthermore, MaOFPs genes duplicates were found to have originated from whole-genome duplication (WGD). The expression patterns of the genes in the various tissues and at different fruit development and ripening stages in the BaXi Jiao (BX) and Feng Jiao (FJ), banana cultivars were elucidated using transcriptome analysis. Using co-expression network analysis, MaOFP1 was found to interact not only with MaMADS36 but also with hormone response proteins. These findings improve our understanding of the functions of MaOFPs genes in the control of plant hormone signal transduction pathways during banana growth and ripening, which should inform the genetic improvement of important agricultural characters.

High-performance ferroelectric non-volatile memory based on La-doped BiFeO3 thin films.

An ultrathin (6.2 nm) ferroelectric La0.1Bi0.9FeO3 (LBFO) film was epitaxially grown on a 0.7 wt% Nb-doped SrTiO3 (001) single-crystal substrate by carrying out pulsed laser deposition to form a Pt/La0.1Bi0.9FeO3/Nb-doped SrTiO3 heterostructure. The LBFO film exhibited strong ferroelectricity and a low coercive field. By optimizing the thickness of the LBFO film, a resistance OFF/ON ratio of the Pt/LBFO (∼6.2 nm)/NSTO heterostructure of as large as 2.8 × 105 was achieved. The heterostructure displayed multi-level storage and excellent retention characteristics, and showed stable bipolar resistance switching behavior, which can be well applied to ferroelectric memristors. The resistance switching behavior was shown to be due to the modulating effect of the ferroelectric polarization reversal on the width of the depletion region and the height of the potential barrier of the LaBiFeO3/Nb-doped SrTiO3 interface.

Identification, Expression, and Interaction Network Analyses of the CDPK Gene Family Reveal Their Involvement in the Development, Ripening, and Abiotic Stress Response in Banana.

Calcium-dependent protein kinases (CDPKs) play vital roles in the regulation of plant growth, development, and tolerance to various abiotic stresses. However, little information is available for this gene family in banana. In this study, 44 CDPKs were identified in banana and were classified into four groups based on phylogenetic, gene structure, and conserved motif analyses. The majority of MaCDPKs generally exhibited similar expression patterns in the different tissues. Transcriptome analyses revealed that many CDPKs showed strong transcript accumulation at the early stages of fruit development and postharvest ripening in both varieties. Interaction network and co-expression analysis further identified some CDPKs-mediated network that was potentially active at the early stages of fruit development. Comparative expression analysis suggested that the high levels of CDPK expression in FJ might be related to its fast ripening characteristic. CDPK expression following the abiotic stress treatments indicated a significant transcriptional response to osmotic, cold, and salt treatment, as well as differential expression profiles, between BX and FJ. The findings of this study elucidate the transcriptional control of CDPKs in development, ripening, and the abiotic stress response in banana. Some tissue-specific, development/ripening-dependent, and abiotic stress-responsive candidate MaCDPK genes were identified for further genetic improvement of banana.

An aquaporin gene MaPIP2-7 is involved in tolerance to drought, cold and salt stresses in transgenic banana (Musa acuminata L.).

Aquaporins (AQPs) transport water and other small molecules; however, their precise role in abiotic stress responses is not fully understood. In this study, we cloned and characterized the PIP2 group AQP gene, MaPIP2-7, in banana. MaPIP2-7 expression was upregulated after osmotic (mannitol), cold, and salt treatments. Overexpression of MaPIP2-7 in banana improved tolerance to multiple stresses such as drought, cold, and salt. MaPIP2-7 transgenic plants showed lower levels of malondialdehyde (MDA) and ion leakage (IL), but higher contents of chlorophyll, proline, soluble sugar, and abscisic acid (ABA) compared with wild type (WT) plants under stress and recovery conditions. Additionally, MaPIP2-7 overexpression decreased cellular contents of Na+ and K+ under salt and recovery conditions, and produced an elevated K+/Na+ ratio under recovery conditions. Finally, ABA biosynthetic and responsive genes exhibited higher expression levels in transgenic lines relative to WT under stress conditions. Taken together, our results demonstrate that MaPIP2-7 confers tolerance to drought, cold, and salt stresses by maintaining osmotic balance, reducing membrane injury, and improving ABA levels.

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.