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.

Effect of deformation of diamond anvil and sample in diamond anvil cell on the thermal conductivity measurement

Studies show that the sample thickness is an important parameter in investigating the thermal transport properties of materials under high-temperature and high-pressure(HTHP)in the diamond anvil cell(DAC)device.However,it is an enormous challenge to measure the sample thickness accurately in the DAC under severe working conditions.In conventional methods,the influence of diamond anvil deformation on the measuring accuracy is ignored.For a hightemperature anvil,the mechanical state of the diamond anvil becomes complex and is different from that under the static condition.At high temperature,the deformation of anvil and sample would be aggravated.In the present study,the finite volume method is applied to simulate the heat transfer mechanism of stable heating DAC through coupling three radiativeconductive heat transfer mechanisms in a high-pressure environment.When the temperature field of the main components is known in DAC,the thermal stress field can be analyzed numerically by the finite element method.The obtained results show that the deformation of anvil will lead to the obvious radial gradient distribution of the sample thickness.If the top and bottom surfaces of the sample are approximated to be flat,it will be fatal to the study of the heat transport properties of the material.Therefore,we study the temperature distribution and thermal conductivity of the sample in the DAC by thermal-solid coupling method under high pressure and stable heating condition.

Investigating the thermal conductivity of materials by analyzing the temperature distribution in diamond anvils cell under high pressure

Investigating the thermal transport properties of materials is of great importance in the field of earth science and for the development of materials under extremely high temperatures and pressures.However,it is an enormous challenge to characterize the thermal and physical properties of materials using the diamond anvil cell(DAC)platform.In the present study,a steady-state method is used with a DAC and a combination of thermocouple temperature measurement and numerical analysis is performed to calculate the thermal conductivity of the material.To this end,temperature distributions in the DAC under high pressure are analyzed.We propose a three-dimensional radiative-conductive coupled heat transfer model to simulate the temperature field in the main components of the DAC and calculate in situ thermal conductivity under high-temperature and high-pressure conditions.The proposed model is based on the finite volume method.The obtained results show that heat radiation has a great impact on the temperature field of the DAC,so that ignoring the radiation effect leads to large errors in calculating the heat transport properties of materials.Furthermore,the feasibility of studying the thermal conductivity of different materials is discussed through a numerical model combined with locally measured temperature in the DAC.This article is expected to become a reference for accurate measurement of in situ thermal conductivity in DACs at high-temperature and high-pressure conditions.

Associations between Placental Insulin-Like Growth Factor-1 Gene Expression, DNA Methylation and Intrauterine Growth Restriction

Intrauterine growth restriction (IUGR) is a common fetal development disorder which has great impact on neonatal health. Insulin-like growth factor-1 (IGF1) has an important role in regulating fetal growth. Whether IGF1 DNA methylation was associated with IUGR has not been studied. Placenta samples from IUGR (n = 27) and normal delivery (n = 29) were collected whereas basic information of mothers and infants were also collected. RT-PCR was performed to examine IGF1 transcriptions and bisulfite sequencing PCR was used for DNA methylation analysis. Gene expression analysis found IUGR had significantly lower IGF1 transcription compared to control group (IUGR: 0.330 ± 0.351;control group: 1.001 ± 0.800, t = 3.995, P IGF1 were all highly methylated and there is no difference on DNA methylation rate between IUGR and control group (IUGR: 75%;control group: 81%;P = 0.09). Interestingly, in both IUGR and control groups, male fetus had significantly higher methylation rate than female fetus (IUGR: male: 87%;female: 74%, P = 0.016;control: male: 82%;female: 69%, P = 0.012). There was no correlation between IGF1gene expression and DNA methylation rate (r = 0.095, P = 0.063). Intrauterine fetal growth restriction placenta had significantly lower IGF1gene expression;however, IGF1 DNA methylation level was similar. A potential fetus gender difference was also found in IGF1 DNA methylation rate.

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.

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.