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.

MaDREB1F confers cold and drought stress resistance through common regulation of hormone synthesis and protectant metabolite contents in banana

Adverse environmental factors severely affect crop productivity.Improving crop resistance to multiple stressors is an important breeding goal.Although CBFs/DREB1s extensively participate in plant resistance to abiotic stress,the common mechanism underlying CBFs/DREB1s that mediate resistance to multiple stressors remains unclear.Here,we show the common mechanism for MaDREB1F conferring cold and drought stress resistance in banana.MaDREB1F encodes a dehydration-responsive element binding protein(DREB)transcription factor with nuclear localization and transcriptional activity.MaDREB1F expression is significantly induced after cold,osmotic,and salt treatments.MaDREB1F overexpression increases banana resistance to cold and drought stress by common modulation of the protectant metabolite levels of soluble sugar and proline,activating the antioxidant system,and promoting jasmonate and ethylene syntheses.Transcriptomic analysis shows that MaDREB1F activates or alleviates the repression of jasmonate and ethylene biosynthetic genes under cold and drought conditions.Moreover,MaDREB1F directly activates the promoter activities of MaAOC4 and MaACO_(2)0 for jasmonate and ethylene syntheses,respectively,under cold and drought conditions.MaDREB1F also targets the MaERF11 promoter to activate MaACO_(2)0 expression for ethylene synthesis under drought stress.Together,our findings offer new insight into the common mechanism underlying CBF/DREB1-mediated cold and drought stress resistance,which has substantial implications for engineering cold-and drought-tolerant crops.

Effect of Banana Stalk Organic Fertilizer on the Growth of Chinese Cabbage

In order to solve the problem of waste disposal after banana harvest,we use banana stalk to produce banana stalk organic fertilizer,through a plot experiment. We compare the influence of normal organic fertilizer( Wanlubao) and banana stalk organic fertilizer as base fertilizers on Chinese cabbage growth,and evaluate the economic benefits of banana stalk organic fertilizer. The results show that organic fertilizer has little effect on water content and nutrient content of Chinese cabbage,but has significant effect on plant height and leaf width. Using organic fertilizer can increase the production of Chinese cabbage by 22. 50%- 43. 10%. With 6750 kg / ha normal organic fertilizer,Chinese cabbage gets the highest yield,which reaches 30135 kg / ha,followed by the treatment of 6750 kg / ha stalk organic fertilizer. At farmers' conventional fertilization level( 4500 kg / ha),stalk organic fertilizer can increase the yield by more than 3. 50% in comparison with the normal organic fertilizer,and the economic benefit increases by 1800 yuan / ha. As a kind of banana waste cycling product,banana stalk organic fertilizer is of low cost and good effect,and can be used instead of normal organic fertilizer.

DFIG Voltage Control Based on Dynamically Adjusted Control Gains

The increasing penetration of wind power presents many technical challenges to power system operations. An important challenge is the need of voltage control to maintain the terminal voltage of a wind plant to make it a PV bus like conventional generators with excitation control. In the previous work for controlling wind plant, especially the Doubly Fed Induction Generator (DFIG) system, the proportional-integral (PI) controllers are popularly applied. These approaches usually need to tune the PI controllers to obtain control gains as a tradeoff or compromise among various operating conditions. In this paper, a new voltage control approach based on a different philosophy is presented. In the proposed approach, the PI control gains for the DFIG system are dynamically adjusted based on the dynamic, continuous sensitivity which essentially indicates the dynamic relationship between the change of control gains and the desired output voltage. Hence, this control approach does not require any good estimation of fixed control gains because it has the self-learning mechanism via the dynamic sensitivity. This also gives the plug-and-play feature of DFIG controllers to make it promising in utility practices. Simulation results verify that the proposed approach performs as expected under various operating conditions.

Banana somatic embryogenesis and biotechnological application

As one of the most important economic crops for both staple food and fruit widely cultivated in the tropics and subtropics,banana(Musa spp.)is susceptible to a plethora of abiotic and biotic stresses.Breeding cultivars resistant to abiotic and biotic stressors without adverse effects on yield and fruit quality are the objectives of banana improvement programs.However,conventional breeding approaches are time-consuming and severely hampered by inherent banana problems(polyploidy and sterility).Therefore,genetic transformation is becoming increasingly popular and can provide rapid solutions.Numerous efforts have been made to develop superior banana cultivars with better resistance to abiotic and biotic stresses and optimum yields using genetic modification strategies.Somatic embryogenesis(SE)through embryogenic cell suspension(ECS)cultures is an ideal recipient system for genetic transformation in banana.The purpose of this paper is to review the current status of banana somatic embryo research,clarify the process of banana somatic embryo induction and culture,and summarize the main influencing factors in the process of somatic embryogenesis.At the same time,their applications in breeding technologies such as cryopreservation,protoplast culture,genetic transformation and gene editing were also summarized,in order to provide reference for the research and practical application of banana somatic embryogenesis in the future.

Allele-defined genome reveals biallelic differentiation during cassava evolution

Dear Editor,Generation of heterozygous genomes by hybridization between or within species can help maintain plant diversity and serve as a potential source of new species(Baek et al.,2018).Moreover,genomic heterozygosity is associated with genomic coadaptation,developmental stability,and heterosis.Accurate definition of alleles in haplotypes is necessary to precisely characterize allelic variation controlling agriculturally important traits(Shi et al.,2019).Currently,most released genomes have mosaic assembly of haplotypes due to random selection or collapse of alleles during genome assembly(Shi et al.,2019),which masked allelic variation and functional differentiation of divergent alleles in heterozygous species.

Genome-wide identification and expression analysis of the β-amylase genes strongly associated with fruit development,ripening, and abiotic stress response in two banana cultivars

β-amylase(BAM) is an important enzyme involved in conversion of starch to maltose in multiple biological processes in plants. However, there is currently insufficient information on the BAM gene family in the important fruit crop banana. This study identified 16 BAM genes in the banana genome. Phylogenetic analysis showed that Ma BAMs were classified into four subfamilies. Most Ma BAMs in each subfamily shared similar gene structures. Conserved motif analysis showed that all identified Ma BAM proteins had the typical glyco hydro14 domains. Comprehensive transcriptomic analysis of two banana genotypes revealed the expression patterns of Ma BAMs in different tissues, at various stages of fruit development and ripening, and in responses to abiotic stresses. Most Ma BAMs showed strong transcript accumulation changes during fruit development and late-stage ripening. Some Ma BAMs showed significant changes under cold, salt, and osmotic stresses. This finding indicated that Ma BAMs might be involved in regulating fruit development, ripening, and responses to abiotic stress. Analysis of five hormone-related and seven stressrelevant elements in the promoters of Ma BAMs further revealed that BAMs participated in various biological processes. This systemic analysis provides new insights into the transcriptional characteristics of the BAM genes in banana and may serve as a basis for further functional studies of such genes.

Cold stress responsive microRNAs and their targets in Musa balbisiana

Cold stress is an environmental factor affecting plant development and production. Recently,micro RNAs(mi RNAs) have been found to be involved in several plant processes such as growth regulation and stress responses. Although mi RNAs and their targets have been identified in several banana species, their participation during cold accumulation in banana remains unknown. In this study, two small RNA libraries were generated from micropropagated plantlets of Musa balbisiana grown at normal and low temperature(5°C).A total of 69 known mi RNAs and 32 putative novel mi RNAs were detected in the libraries by Solexa sequencing. Sixty-four cold-inducible mi RNAs were identified through differentially expressed mi RNAs analysis. Among 43 mi RNAs belonging to 26 conserved mi RNA families with altered expression, 18 were upregulated and 25 downregulated under cold stress. Of21 putative novel mi RNAs with altered expression, four were downregulated and 17 upregulated. Furthermore,eight mi RNAs were validated by stem-loop q RT-PCR and their dynamic differential expression was analyzed. In addition, 393 target genes of 58 identified cold-responsive mi RNAs were predicted and categorized by function.These results provide important information for further characterization and functional analysis of cold-responsive mi RNAs in banana.

Hollow-core fiber-based Raman probe extension kit for in situ and sensitive ultramicro-analysis

A metal-lined hollow-core fiber-based Raman probe extension kit is proposed in this Letter for in situ and sensitive ultramicro-analysis. A hollow-core fiber can confine light and fluid samples in its hollow core, with enhanced light–sample interaction. By using a homemade light coupling device with a glass window for liquid isolation, a 3.5-cm-long hollow-core fiber could mount on and connect to a Raman probe, with perfect light coupling efficiency. After full filling the hollow-core fiber chamber with a volume of 13 μL by using a syringe pump, it can act as an extension kit for an ordinary Raman probe and be used as a ultramicro-analysis tool for the sample of microfluidic chips. In order to enhance its sensitivity, a gold film coated fiber tip is inserted into the capillary, which can double the Raman signal received by reflecting pump light and Raman light. Finally, a detection limit of 5% for ethanol solution and an enhancement factor of two compared with direct detection of bulk sample volume are demonstrated. Above all, our device can be utilized as a Raman probe extension kit, which is suitable for rapid, sensitive, and in situ measurements for a few microliter level samples.

Efficient regeneration system applicable to five Musa cultivars

Banana(Musa spp.) is an important staple food, economic crop, and nutritional fruit worldwide.Hybridization is seriously hampered by the long generation time, polyploidy, and sterility of most cultivars.Establishment of an efficient regeneration and transformation system for banana is critical for their genetic improvement. An efficient and reproducible transformation system for banana using direct organogenesis was developed. Media containing benzylaminopurine(BA)combined with one of four other growth regulators was evaluated for the regeneration efficiency of five Musa cultivars and the ability to induce/support development of new banana shoots. The result indicated that the greatest number of shoots per explant for all five Musa cultivars was obtained using MS medium supplemented with8.9 mmol$L–1BA and 9.1 mmol$L–1thidiazuron(TDZ).In 240–270 d, one immature male flower could regenerate between 380 and 456, 310–372, 200–240, 130–156, and100–130 well-developed shoots for Gongjiao, Red banana, Rose banana, Baxi, and Xinglongnaijiao, respectively. Such a system will facilitate molecular breeding and functional genomics of banana.