Banana Cells Research Articles

A virulent milRNA inhibits host immunity by silencing a host receptor-like kinase MaLYK3 and facilitates infection by Fusarium oxysporum f. sp. cubense.

MicroRNA-like RNAs (milRNAs) play a significant role in the infection process by plant-pathogenic fungi. However, the specific functions and regulatory mechanisms of fungal milRNAs remain insufficiently elucidated. This study investigated the function of Foc-milR138, an infection-induced milRNA secreted by Fusarium oxysporum f. sp. cubense (Foc), which is the causal agent of Fusarium wilt of banana. Initially, through precursor gene knockout and phenotypic assessments, we confirmed that Foc-milR138 acts as a virulent milRNA prominently upregulated during the early stages of Foc infection. Subsequent bioinformatic analyses and transient expression assays in Nicotiana benthamiana leaves identified a host receptor-like kinase gene, MaLYK3, as the direct target of Foc-milR138. Functional investigations of MaLYK3 revealed its pivotal role in triggering immune responses of N. benthamiana by upregulating a suite of resistance genes, bolstering reactive oxygen species (ROS) accumulation and callose deposition, thereby fortifying disease resistance. This response was markedly subdued upon co-expression with Foc-milR138. Expression pattern analysis further verified the specific suppression of MaLYK3 by Foc-milR138 during the early root infection by Foc. In conclusion, Foc secretes a virulent milRNA (Foc-milR138) to enter the host banana cells and inhibit the expression of the plant surface receptor-like kinase MaLYK3, subverting the disease resistance activated by MaLYK3, and ultimately facilitating pathogen invasion. These findings shed light on the roles of fungal milRNAs and their targets in resistance and pathogenicity, offering promising avenues for the development of disease-resistant banana cultivars.

Lipid metabolism and MAPK-ICE1 cascade play crucial roles in cold tolerance of banana

Low temperature is a major environmental factor that limits the growth, yield, and geographical distribution of Cavendish and Dajiao bananas (Musa spp.). Dajiao bananas exhibit a significantly higher cold tolerance than the Cavendish cultivar. However, the underlying mechanisms involved in cold tolerance regulation in Dajiao plants have not been determined. In this study, we investigated the mechanisms underlying the differences in cold tolerance at the cellular level between the cold-sensitive Cavendish and cold-tolerant Dajiao banana types through comparative metabolomics and transcriptomics analyses in calli exposed to cold treatment under dark conditions. A higher accumulation of lipids was observed in Dajiao calli cells compared to Cavendish cells under cold stress. After cold treatment, 4,626 and 5,516 differentially expressed genes (DEGs) were identified in Cavendish and Dajiao banana cells, respectively. By integrating the transcriptomic and metabolomic datasets, we discovered that the linoleic acid and α-linoleic acid metabolism and the Abscisic acid (ABA)-independent Mitogen-activated protein kinase (MAPK) cascade-Inducer of CBF expression 1 (ICE1) signal transduction pathway (including Mitogen-activated protein kinase kinase kinase 1 [MEKK1], MAPK5, ICE1, and Cold-regulated 47 [COR47]) played crucial roles in the cold tolerance of Dajiao bananas. Our study provides new insights into cold response regulation and novel cold tolerance mechanisms, providing valuable leads and targets for the genetic improvement of cold tolerance in bananas.

Active longitudes and the structure of the large-scale magnetic field at solar minimum

We have studied deep minima of 11-year solar activity cycles 13–14, 14–15, 22–23, 23–24, 24–25, using the RGO and USAF/NOAA sunspot group catalogs. All of them have a large number of spotless days. Nonetheless, active longitudes as preferred zones, where sunspots occur, appear at this solar cycle phase. Analysis of synoptic maps and WSO daily magnetograms reflecting the structure of a weak large-scale field shows a non-axisymmetric component of the solar magnetic field. At solar minimum in the structure of the large-scale magnetic field, there are regions of the magnetic field of positive and negative polarity elongated along the meridian and crossing the equator. The most pronounced of them are located in the zone of active longitudes and are often connected with the polar magnetic fields.
 We discuss the possible nature of the meridional structures of the large-scale field during solar minimum. This might be due to giant convection cells with a banana cell structure.

Активные долготы и структура крупномасштабного магнитного поля в минимуме солнечной активности

We have studied deep minima of 11-year solar activity cycles 13–14, 14–15, 22–23, 23–24, 24–25, using the RGO and USAF/NOAA sunspot group catalogs. All of them have a large number of spotless days. Nonetheless, active longitudes as preferred zones, where sunspots occur, appear at this solar cycle phase. Analysis of synoptic maps and WSO daily magnetograms reflecting the structure of a weak large-scale field shows a non-axisymmetric component of the solar magnetic field. At solar minimum in the structure of the large-scale magnetic field, there are regions of the magnetic field of positive and negative polarity elongated along the meridian and crossing the equator. The most pronounced of them are located in the zone of active longitudes and are often connected with the polar magnetic fields.
 We discuss the possible nature of the meridional structures of the large-scale field during solar minimum. This might be due to giant convection cells with a banana cell structure.

Different responses of banana classical AGP genes and cell wall AGP components to low-temperature between chilling sensitive and tolerant cultivars.

Seventeen classical MaAGPs and 9 MbAGPs were identified and analyzed. MaAGP1/2/6/9/16/17, the antigens of JIM13 and LM2 antibodies are likely to be involved in banana chilling tolerance. Classical arabinogalactan proteins (AGPs) belong to glycosylphosphatidylinositol-anchored proteins, which are proved to be involved in signaling and cell wall metabolism upon stresses. However, rare information is available on the roles of classical AGPs in low temperature (LT) tolerance. Cultivation of banana in tropical and subtropical region is seriously threatened by LT stress. In the present study, 17 classical MaAGPs and nine MbAGPs in banana A and B genome were identified and characterized, respectively. Great diversity was present among different classical MaAGP/MbAGP members while five members (AGP3/6/11/13/14) showed 100% identity between these two gene families. We further investigated different responses of classical AGPs to LT between a chilling sensitive (CS) and tolerant (CT) banana cultivars. In addition, different changes in the temporal and spatial distribution of cell wall AGP components under LTs between these two cultivars were compared using immunofluorescence labeling. Seven classical MbAGPs were upregulated by LT(s) in the CT cultivar. Classical MaAGP4/6 was induced by LT(s) in both cultivars while MaAGP1/2/9/16/17 only in the CT cultivar. Moreover, these genes showed significantly higher transcription abundance in the CT cultivar than the CS one under LT(s) except classical MaAGP4. Similar results were observed with the epitopes of JIM13 and LM2 antibodies. The antigens of these antibodies and classical MaAGP1/2/6/9/16/17 might be related to LT tolerance of banana. These results provide additional information about plant classical AGPs and their involvement in LT tolerance, as well as their potential as candidate genes to be targeted when breeding CT banana.

Theory of solar oscillations in the inertial frequency range: Linear modes of the convection zone

Context. Several types of global-scale inertial modes of oscillation have been observed on the Sun. These include the equatorial Rossby modes, critical-latitude modes, and high-latitude modes. However, the columnar convective modes (predicted by simulations and also known as banana cells or thermal Rossby waves) remain elusive. Aims. We aim to investigate the influence of turbulent diffusivities, non-adiabatic stratification, differential rotation, and a latitudinal entropy gradient on the linear global modes of the rotating solar convection zone. Methods. We numerically solved for the eigenmodes of a rotating compressible fluid inside a spherical shell. The model takes into account the solar stratification, turbulent diffusivities, differential rotation (determined by helioseismology), and the latitudinal entropy gradient. As a starting point, we restricted ourselves to a superadiabaticity and turbulent diffusivities that are uniform in space. We identified modes in the inertial frequency range, including the columnar convective modes as well as modes of a mixed character. The corresponding mode dispersion relations and eigenfunctions are computed for azimuthal orders of m ≤ 16. Results. The three main results are as follows. Firstly, we find that, for m ≳ 5, the radial dependence of the equatorial Rossby modes with no radial node (n = 0) is radically changed from the traditional expectation (rm) for turbulent diffusivities ≳1012 cm2 s−1. Secondly, we find mixed modes, namely, modes that share properties of the equatorial Rossby modes with one radial node (n = 1) and the columnar convective modes, which are not substantially affected by turbulent diffusion. Thirdly, we show that the m = 1 high-latitude mode in the model is consistent with the solar observations when the latitudinal entropy gradient corresponding to a thermal wind balance is included (baroclinically unstable mode). Conclusions. To our knowledge, this work is the first realistic eigenvalue calculation of the global modes of the rotating solar convection zone. This calculation reveals a rich spectrum of modes in the inertial frequency range, which can be directly compared to the observations. In turn, the observed modes can inform us about the solar convection zone.

Identification of putative viroplasms within banana cells infected by banana streak MY virus.

The badnavirus replication cycle is poorly understood and most knowledge is based on extrapolations from model viruses such as Cauliflower mosaic virus (CaMV). However, in contrast to CaMV, badnaviruses are thought not to produce viroplasms and therefore it has been a mystery as to where virion assembly occurs. In this study, ultrathin sections of a banana leaf infected with a badnavirus, banana streak MY virus (BSMYV), were examined by transmission electron microscopy. Electron-dense inclusion bodies (EDIBs) were sporadically distributed in parenchymatous tissues of the leaf, most commonly in the palisade and spongy mesophyll cells. These EDIBs had a characteristic structure, comprising an electron-dense core, a single, encircling lacuna and an outer ring of electron-dense material. However, much less frequently, EDIBs with two or three lacunae were observed. In the outer ring, densely packed virions were visible with a shape and size consistent with that expected for badnaviruses. Immunogold labelling was done with primary antibodies that detected the N-terminus of the capsid protein and strong labelling of the outer ring but not the central core or lacuna was observed. It is concluded that the EDIBs that were observed are equivalent in function to the viroplasms of CaMV, although obviously different in composition as there is not a paralogue of the transactivation/viroplasm protein in the badnavirus genome. It is postulated that production of a viroplasm could be a conserved characteristic of all members of the Caulimoviridae.

ANALISIS BROWNING BUAH PISANG KEPOK (Musa paradisiaca L.) SETELAH PERLAKUAN ASAM ASKORBAT DAN LIDAH BUAYA (Aloe barbadensis L.)

Fruit is a necessity for most Indonesian people. Kepok banana is a climacteric fruit that can experience browning quickly. Therefore, this study was conducted to find a safe and effective material to prevent the browning process of kepok bananas. This study aims to determine the differences in the browning index, and the activity of the enzyme dehydrogenase in kepok banana cells. This study was conducted using a 2x3 factorial design. Factor A is ascorbic acid with 2 concentration levels namely 0% (b / v) and 5% (b / v). Factor B is Aloe (Aloebarbadensis L.) leaf extract with 3 levels, namely 0%, 5%, and 10%. The quantitative parameters are browning index and total dissolved carbohydrate content. The qualitative parameter is dehydrogenase enzyme activity. Levene test and variance analysis were carried out with 5% real level. The results obtained were kepok bananas with treatments coloured brighter than control. Ascorbic acid and Aloe (Aloe barbadensis L.) affect the browning index and dissolved total carbohydrate content of the sample. A decrease in dehydrogenase enzyme activity happened in the ascorbic acid treatment. Conclusions obtained from the study are ascorbic acid with a concentration of 5% can reduce the browning index of kepok banana by 31%, ascorbic acid with a concentration of 5% can maintain total dissolved carbohydrate content kepok banana as much as 53%, and Aloe extract 10% retain total dissolved carbohydrate content sample is 20%.

English

Gene transfer into the plant cell is a key step towards its successful genetic modification and its efficiency is heavily dependent on plant and bacterial cell biological status and a wide array of physical conditions. Gene transfer efficiencies in East African Highland Banana (EAHB) cell lines remains low compared to other monocotyledonous crops like rice and wheat due to factors such as high oxidative stress. The use of antioxidants is fundamental in influencing gene transfer events during Agrobacterium-plant cell co-cultivation. Here we report significant enhancement of gene transfer efficiency in the EAHB cultivar ‘Nakinyika’ (EA-AAA) by supplementing co-cultivation medium with antioxidants; ascorbic acid (AA), glutathione (GSH), tocopherol (TOC) and silver nitrate (SN). The most enhancing antioxidant by number of blue foci after histochemical assay, as a parameter of gene transfer efficiency, was ascorbic acid (174 cells) at a concentration of 40 mg/L, followed by glutathione (91 cells) and tocopherol (91 cells) both at 50 mg/L. The least enhancement was observed when ascorbic acid (39 cells), silver nitrate (41 and 31 cells) were used at concentrations of 20, 4 and 6 mg/L compared to 72 cells in controls (no anti-oxidants).  Regeneration efficiency increased from 29 cells in controls to 46% for SN at 8 mg/L; 43% for GSH at 100 mg/L; 30% for TOC at 75 mg/L; and 48% for AA at 20 mg/L. Polymerase chain reaction (PCR) results using gusA specific primers showed that these regenerants were putative transformants and grew normally during regeneration, rooting and multiplication. GSH and TOC significantly enhanced gene transfer efficiency while AA and SN showed significant increases in shoot regeneration compared to controls. The current results show that antioxidants significantly enhance gene transfer and regeneration efficiency in recalcitrant banana cell lines and could significantly enhance the overall transformation efficiencies in cases where numerous transgenic lines are required in a short time.   Key words: Highland bananas, transgenic, browning, transformation efficiency, agrobacterium.

Cell Wall Polymer Composition and Spatial Distribution in Ripe Banana and Mango Fruit: Implications for Cell Adhesion and Texture Perception.

Banana (Musa acuminata) and mango (Mangifera indica) are two of the most popular fruits eaten worldwide. They both soften during ripening but their textural attributes are markedly different. This study aimed to elucidate the molecular mechanism underpinning textural differences between banana and mango. We used a novel combination of methods at different scales to analyse the surface properties of fruit cells and the potential contribution of cells and cell wall components to oral processing and texture perception. The results indicated that cell separation occurred easily in both organs under mild mechanical stress. Banana cells showed distinctively elongated shapes with distinct distribution of pectin and hemicellulose epitopes at the cell surface. In contrast, mango had relatively spherical cells that ruptured during cell separation. Atomic force microscopy detected soft surfaces indicative of middle lamella remnants on banana cells, while mango cells had cleaner, smoother surfaces, suggesting absence of middle lamellae and more advanced cell wall disassembly. Comparison of solubilized polymers by cell wall glycome analysis showed abundance of mannan and feruylated xylan in separation exudate from banana but not mango, but comparable levels of pectin and arabinogalactan proteins. Bulk rheology experiments showed that both fruits had similar apparent viscosity and hence might be extrapolated to have similar “oral thickness” perception. On the other hand, oral tribology experiments showed significant differences in their frictional behavior at orally relevant speeds. The instrumental lubrication behavior can be interpreted as “smooth” mouthfeel for mango as compared to “astringent” or “dry” for banana in the later stages of oral processing. The results suggest that cell wall surface properties contribute to lubricating behavior associated with textural perception in the oral phase.

Driving Solar Giant Cells through the Self-organization of Near-surface Plumes

Abstract Global 3D simulations of solar giant-cell convection have provided significant insight into the processes which yield the Sun’s observed differential rotation and cyclic dynamo action. However, as we move to higher-resolution simulations a variety of codes have encountered what has been termed the convection conundrum. As these simulations increase in resolution and hence the level of turbulence achieved, they tend to produce weak or even anti-solar differential rotation patterns associated with a weak rotational influence (high Rossby number) due to large convective velocities. One potential culprit for this convection conundrum is the upper boundary condition applied in most simulations, which is generally impenetrable. Here we present an alternative stochastic plume boundary condition which imposes small-scale convective plumes designed to mimic near-surface convective downflows, thus allowing convection to carry the majority of the outward solar energy flux up to and through our simulated upper boundary. The use of a plume boundary condition leads to significant changes in the convective driving realized in the simulated domain and thus to the convective energy transport, the dominant scale of the convective enthalpy flux, and the relative strength of the strongest downflows, the downflow network, and the convective upflows. These changes are present even far from the upper boundary layer. Additionally, we demonstrate that, in spite of significant changes, giant cell morphology in the convective patterns is still achieved with self-organization of the imposed boundary plumes into downflow lanes, cellular patterns, and even rotationally aligned banana cells in equatorial regions. This plume boundary presents an alternative pathway for 3D global convection simulations where driving is non-local and may provide a new approach toward addressing the convection conundrum.

Dynamic effects of restoring footpoint symmetry on closed magnetic field lines

AbstractHere we present an event where simultaneous global imaging of the aurora from both hemispheres reveals a large longitudinal shift of the nightside aurora of about 3 h, being the largest relative shift reported on from conjugate auroral imaging. This is interpreted as evidence of closed field lines having very asymmetric footpoints associated with the persistent positive y component of the interplanetary magnetic field before and during the event. At the same time, the Super Dual Auroral Radar Network observes the ionospheric nightside convection throat region in both hemispheres. The radar data indicate faster convection toward the dayside in the dusk cell in the Southern Hemisphere compared to its conjugate region. We interpret this as a signature of a process acting to restore symmetry of the displaced closed magnetic field lines resulting in flux tubes moving faster along the banana cell than the conjugate orange cell. The event is analyzed with emphasis on Birkeland currents (BC) associated with this restoring process, as recently described by Tenfjord et al. (2015). Using data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) during the same conditions as the presented event, the large‐scale BC pattern associated with the event is presented. It shows the expected influence of the process of restoring symmetry on BCs. We therefore suggest that these observations should be recognized as being a result of the dynamic effects of restoring footpoint symmetry on closed field lines in the nightside.

Microbial biotransformation of polyphenols during in vitro colonic fermentation of masticated mango and banana

Mango and banana cell structures, which survived in vivo mastication and in vitro gastrointestinal digestion, were fermented in vitro for 48h. For both fruits, flavonoids and phenolic acids were liberated and underwent microbial metabolism involving ring fission, dehydroxylation and decarboxylation. UHPLC-PDA/Q-ToF-MS profiles revealed rapid degradation (72–78%) of most intact precursors (epicatechin and several unidentified compounds) within 10h, before the exponential phase of the cumulative gas production. Concomitant formation of catabolites (e.g. 4-hydroxyphenylacetic acid) occurred within 4–8h, while metabolism of catechin derivative and 3-(4-hydroxyphenyl)propanoic acid continued slowly for at least 48h, suggesting intact plant cell walls can be a controlling factor in microbial susceptibility. Untargeted PCA and OPLS-DA demonstrated clear classifications in the compositional fruit type and compound profiles as a function of time. Clusters and distinct discriminating compounds were recognised, which could lead to subsequent biomarker identification for establishing differences in polyphenol microbial metabolism of various fruit matrices.

Exploring Carbohydrates with Bananas

Bananas can be used in many classroom lab activities to make carbohydrates easier for students to understand. I detail a simple series of banana activities that can be used to investigate carbohydrates across a wide range of levels of organization and that serve to connect carbohydrate concepts that might otherwise seem disparate to students. For example, the taste of a banana is linked to carbohydrate hydrolysis, as well as to organelle content within banana cells. Bananas can be used safely in any classroom, and inquiry-based learning can be used to progress through related course content. In addition, students will gain expertise in understanding cells viewed through the microscope as they try to examine the starch in the bananas.

HIGH-RESOLUTION CALCULATION OF THE SOLAR GLOBAL CONVECTION WITH THE REDUCED SPEED OF SOUND TECHNIQUE. II. NEAR SURFACE SHEAR LAYER WITH THE ROTATION

We present a high-resolution, highly stratified numerical simulation of rotating thermal convection in a spherical shell. Our aim is to study in detail the processes that can maintain a near surface shear layer (NSSL) as inferred from helioseismology. Using the reduced speed of sound technique we can extend our global convection simulation to $0.99\,R_{\odot}$ and include near the top of our domain small-scale convection with short time scales that is only weakly influenced by rotation. We find the formation of a NSSL preferentially in high latitudes in the depth range $r=0.95-0.975R_\odot$. The maintenance mechanisms are summarized as follows. Convection under weak influence of rotation leads to Reynolds stresses that transport angular momentum radially inward in all latitudes. This leads to the formation of a strong poleward directed meridional flow and a NSSL, which is balanced in the meridional plane by forces resulting from the $\langle v'_r v'_\theta\rangle$ correlation of turbulent velocities. The origin of the required correlations depends to some degree on latitude. In high latitudes a positive correlation $\langle v'_rv'_\theta\rangle$ is induced in the NSSL by the poleward meridional flow whose amplitude increases with the radius, while a negative correlation is generated by the Coriolis force in bulk of the convection zone. In low latitudes a positive correlation $\langle v'_rv'_\theta\rangle$ results from rotationally aligned convection cells ("banana cells"). The force caused by these Reynolds stresses is in balance with the Coriolis force in the NSSL.

Native cell-death genes as candidates for developing wilt resistance in transgenic banana plants.

In order to feed an ever-increasing world population, there is an urgent need to improve the production of staple food and fruit crops. The productivity of important food and fruit crops is constrained by numerous biotic and abiotic factors. The cultivation of banana, which is an important fruit crop, is severely threatened by Fusarium wilt disease caused by infestation by an ascomycetes fungus Fusarium oxysporum f. sp. cubense (Foc). Since there are no established edible cultivars of banana resistant to all the pathogenic races of Foc, genetic engineering is the only option for the generation of resistant cultivars. Since Foc is a hemibiotrophic fungus, investigations into the roles played by different cell-death-related genes in the progression of Foc infection on host banana plants are important. Towards this goal, three such genes namely MusaDAD1, MusaBAG1 and MusaBI1 were identified in banana. The study of their expression pattern in banana cells in response to Foc inoculation (using Foc cultures or fungal toxins like fusaric acid and beauvericin) indicated that they were indeed differentially regulated by fungal inoculation. Among the three genes studied, MusaBAG1 showed the highest up-regulation upon Foc inoculation. Further, in order to characterize these genes in the context of Foc infection in banana, we generated transgenic banana plants constitutively overexpressing the three genes that were later subjected to Foc bioassays in a contained greenhouse. Among the three groups of transgenics tested, transformed banana plants overexpressing MusaBAG1 demonstrated the best resistance towards Foc infection. Further, these plants also showed the highest relative overexpression of the transgene (MusaBAG1) among the three groups of transformed plants generated. Our study showed for the first time that native genes like MusaBAG1 can be used to develop transgenic banana plants with efficient resistance towards pathogens like Foc.

Evaluation of a laboratory scale conventional shake flask and a bioreactor on cell growth and regeneration of banana cell suspension cultures

It is important to develop a system to enhance the growth and regeneration of cells with limited totipotency into healthy plantlets. In this study, a semi automated cell suspension culture protocol for Musa acuminata cv. Berangan using bioreactor has been established. After eight months of culture, embryogenic calli generated from male inflorescences were transferred to liquid medium. Cell suspension cultures showed better cell growth when cultured in the M2 modified liquid medium containing 2% (w/v) sucrose with an initial inoculum density of 1:50 (cells:medium). The yield of cell suspension cultures was increased to 165% and 210%, respectively, when inoculated in 5l balloon type bubble column bioreactors (BTBCBs) without pH control and with pH maintained at 5.7, over 14 days of culture. It was also shown that the growth yield was 3-fold higher when cultured in pH-controlled BTBCB, followed by 2.5-fold in uncontrolled-pH BTBCB and 2.2-fold in shake flask culture in comparison to initial culture (day 1). In all growth vessels tested, catalase (CAT) activity was found to be correlated with hydrogen peroxide (H2O2) concentration, suggesting its effective scavenging activity, whereas no significant difference was observed for superoxide dismutase (SOD). More than 60% of the embryos started to form shoots after 2 weeks of culture on M4 medium for all growth vessels tested. Potentially, this protocol may help in mass producing disease-free and high yielding banana as it provides a comparable cell growth rate producing normal regenerants in comparison to the conventional shake flask cultures.

Effect of Adding Banana Cell Wall to Fat-Reduced Shortbread Cookie on Dough Hardness and Toughness

The effect of banana cell wall on dough hardness and toughness with 10% fat reduction was investigated. Alcohol insoluble solids containing cell wall (AIS) was prepared from ripe bananas using hot ethanol extraction. Analysis of AIS for monosaccharide composition showed that it contains fucose, rhamnose, arabinose, galactose, glucose, maltose, xylose and mannose, galacturonic acid and glucuronic acid. Changes in hardness and toughness of the dough were analysed using a texture analyser. As the fat content decreased by 10%, the dough hardness was increased to 52.63 N ± 6.33 compared to control (31.29 N ± 2.34). However, the dough hardness was then reduced to 28.36 N ± 3.11 when 0.5 g of banana AIS was added to the dough and this indicates that banana AIS helps to reduce the hardness caused by fat reduction. Similar results were obtained for dough toughness. The addition of banana AIS decreased toughness to 48.16N.sec ±7.54 from 79.99N.sec ± 1.85 in fat reduced dough. In conclusion, banana cell wall has beneficial effects on dough rheology in fat reduced cookie dough.

Transgenic banana plants overexpressing a native plasma membrane aquaporin MusaPIP1;2 display high tolerance levels to different abiotic stresses

Water transport across cellular membranes is regulated by a family of water channel proteins known as aquaporins (AQPs). As most abiotic stresses like suboptimal temperatures, drought or salinity result in cellular dehydration, it is imperative to study the cause-effect relationship between AQPs and the cellular consequences of abiotic stress stimuli. Although plant cells have a high isoform diversity of AQPs, the individual and integrated roles of individual AQPs in optimal and suboptimal physiological conditions remain unclear. Herein, we have identified a plasma membrane intrinsic protein gene (MusaPIP1;2) from banana and characterized it by overexpression in transgenic banana plants. Cellular localization assay performed using MusaPIP1;2::GFP fusion protein indicated that MusaPIP1;2 translocated to plasma membrane in transformed banana cells. Transgenic banana plants overexpressing MusaPIP1;2constitutively displayed better abiotic stress survival characteristics. The transgenic lines had lower malondialdehyde levels, elevated proline and relative water content and higher photosynthetic efficiency as compared to equivalent controls under different abiotic stress conditions. Greenhouse-maintained hardened transgenic plants showed faster recovery towards normal growth and development after cessation of abiotic stress stimuli, thereby underlining the importance of these plants in actual environmental conditions wherein the stress stimuli is often transient but severe. Further, transgenic plants where the overexpression of MusaPIP1;2 was made conditional by tagging it with a stress-inducible native dehydrin promoter also showed similar stress tolerance characteristics in in vitro and in vivo assays. Plants developed in this study could potentially enable banana cultivation in areas where adverse environmental conditions hitherto preclude commercial banana cultivation.

Excision of a selectable marker gene in transgenic banana using a Cre/lox system controlled by an embryo specific promoter

Antibiotic and herbicide resistance genes have been used in transgene technology as powerful selection tools. Nonetheless, once transgenic events have been obtained their presence is no longer needed and can even be undesirable. In this work, we have developed a system to excise the selectable marker and the cre recombinase genes from transgenic banana cv. 'Grande Naine' (Musa AAA). To achieve this, the embryo specific REG-2 promoter was isolated from rice and its expression pattern in banana cell clumps, somatic embryos and regenerated plantlets was characterized by using a pREG2::uidA fusion construct. Subsequently, the REG-2 promoter was placed upstream of the cre gene, conferring Cre functionality in somatic embryos and recombination of lox sites resulting in excision of the selectable marker and cre genes. PCR analysis revealed that 41.7% of the analysed transgenic plants were completely marker free, results that were thereafter confirmed by Southern blot hybridization. These results demonstrate the feasibility of using developmentally controlled promoters to mediate marker excision in banana. This system does not require any extra handling compared to the conventional transformation procedure and might be useful in other species regenerating through somatic embryogenesis.