No abstract

As one of the most important transcription factors regulating plant anthocyanin biosynthesis, MYB has attracted great attentions. In this study, we identified fifteen candidate anthocyanin biosynthesis related MYB (ABRM) proteins, including twelve R2R3-MYBs and three 1R-MYBs, from highbush blueberry. The subcellular localization prediction results showed that, with the exception of VcRVE8 (localized in chloroplast and nucleus), all of the blueberry ABRMs were nucleus-localized. The gene structure analysis revealed that the exon numbers of the blueberry ABRM genes varied greatly, ranging between one and eight. There are many light-responsive, phytohormone-responsive, abiotic stress-responsive and plant growth and development related cis-acting elements in the promoters of the blueberry ABRM genes. It is noteworthy that almost all of their promoters contain light-, ABA- and MeJA-responsive elements, which is consistent with the well-established results that anthocyanin accumulation and the expression of MYBs are influenced significantly by many factors, such as light, ABA and JA. The gene expression analysis revealed that VcMYB, VcMYB6, VcMYB23, VcMYBL2 and VcPH4 are expressed abundantly in blueberry fruits, and VcMYB is expressed the highest in the red, purple and blue fruits among all blueberry ABRMs. VcMYB shared high similarity with functionally proven ABRMs from many other plant species. The gene cloning results showed that VcMYB had three variable transcripts, but only the transient overexpression of VcMYB-1 promoted anthocyanin accumulation in the green fruits. Our study can provide a basis for future research on the anthocyanin biosynthesis related MYBs in blueberry.

As an endophytic fungus, the growth-promoting effects of Piriformospora indica have been widely confirmed in many of its host plants. In this study, we investigated the influences of P. indica colonization on the growth of the daughter plants of two strawberry cultivars, ‘Benihoppe’ and ‘Sweet Charlie.’ The results showed that the fungus colonization significantly promoted the growth of the daughter plants of both of the two strawberry varieties. Its colonization greatly improved almost all of the growth parameters of the ‘Benihoppe’ daughter plants, including the above-ground fresh weight, above-ground dry weight, root fresh weight, root dry weight, plant height, petiole length, leaf area, number of roots and chlorophyll content. However, the fungus colonization showed significant improving effects on only the above-ground fresh weight, root fresh weight and root dry weight of ‘Sweet Charlie.’ Surprisingly, the average root length of ‘Benihoppe’ and ‘Sweet Charlie’ was suppressed by about 14.3% and 24.6%, respectively, by P. indica. Moreover, after P. indica colonization, the leaf nitrate reductase activity and root activity upregulated by 30.12% and 12.74%, and 21.85% and 21.16%, respectively, for the ‘Benihoppe’ and ‘Sweet Charlie’ daughter plants. Our study indicated that P. indica could promote the growth of strawberry daughter plants by improving rooting, strengthening photosynthetic pigments production and nutrient absorption and accelerating biomass accumulation. The fungus shows great potential to be used in the strawberry industry, especially in the breeding of daughter plants.

Recently, many control methods have been tried and applied in the Fusarium wilt disease control of banana and have achieved definite progresses. In this study, by using ‘Zhongjiao No.3’ and ‘Zhongjiao No.4’ banana seedlings as materials, the effects of Serendipita indica and bamboo fungus (Dictyophorae echinovolvata) culture substrates on the growth and Fusarium wilt disease resistance of banana were investigated. Results showed that the plant height, leaf length, leaf width, root length and root thickness, aboveground part fresh weight, root fresh weight, and relative chlorophyll content and nitrogen content in leaves of banana seedlings colonized with S. indica were all greater than those of non-colonized controls, while these parameters of banana seedlings grown in nutrient soil containing D. echinovolvata culture substrates were significantly suppressed. Both S. indica non-colonized and colonized seedlings cultivated in nutrient containing 1/4 D. echinovolvata culture substrates showed much milder symptoms compared with those cultivated in normal nutrient soil, indicating that the addition of bamboo fungus substrates to the soil can enhance the Fusarium wilt resistance of banana. The results obtained in this study can provide a basis for the application of S. indica and bamboo fungus in the prevention and control of banana Fusarium wilt disease.

SNAREs (soluble N-ethylmaleimide-sensitive-factor attachment protein receptors) are engines for almost all of the membrane fusion and exocytosis events in organism cells. In this study, we identified 84 SNARE genes from banana (Musa acuminata). Gene expression analysis revealed that the expression of MaSNAREs varied a lot in different banana organs. By analyzing their expression patterns under low temperature (4 °C), high temperature (45 °C), mutualistic fungus (Serendipita indica, Si) and fungal pathogen (Fusarium oxysporum f. sp. Cubense Tropical Race 4, FocTR4) treatments, many MaSNAREs were found to be stress responsive. For example, MaBET1d was up-regulate by both low and high temperature stresses; MaNPSN11a was up-regulated by low temperature but down-regulated by high temperature; and FocTR4 treatment up-regulated the expression of MaSYP121 but down-regulated MaVAMP72a and MaSNAP33a. Notably, the upregulation or downregulation effects of FocTR4 on the expression of some MaSNAREs could be alleviated by priorly colonized Si, suggesting that they play roles in the Si-enhanced banana wilt resistance. Foc resistance assays were performed in tobacco leaves transiently overexpressing MaSYP121, MaVAMP72a and MaSNAP33a. Results showed that transient overexpression of MaSYP121 and MaSNPA33a suppressed the penetration and spread of both Foc1 (Foc Race 1) and FocTR4 in tobacco leaves, suggesting that they play positive roles in resisting Foc infection. However, the transient overexpression of MaVAMP72a facilitated Foc infection. Our study can provide a basis for understanding the roles of MaSNAREs in the banana responses to temperature stress and mutualistic and pathogenic fungal colonization.