Banana is an important staple crop and widely grown in more than 130 countries around the world. Plant height is one of the major characteristics of crops (Wang et al., 2018), however, the height of commercial banana varieties is more than two meters, and higher varieties are frequently challenged by the weak lodging and severe damages caused by typhoons and storms. Dwarf varieties are suitable for mechanized plant maintenance and fruit harvesting (Dash et al., 2016), thus development of semi‐dwarf and dwarf banana is important to current farming systems.

Banana is a fruit with high nutrient content and high economic importance. It is regarded as a main staple food in developing countries. As a typical climacteric fruit, banana will ripen and decay in one week after exogenous ethylene induction. The short shelf life of banana largely limits its storage, transportation and marketing, and causes great post‐harvest loss (Krishnakumar, T. and Thirupathi, V. 2014). The shelf life of banana is closely related to ethylene production, which is the first factor considered for developing postharvest preservation technology.

Current banana cultivation is facing a serious threat known as Panama disease or Fusarium wilt, which is caused by the Fusarium oxysporum (Dale et al., 2017). To date, development of Fusarium wilt‐resistant banana still faces challenges of various sexual reproduction barriers such as high sterility, complex genetic background, polypoid and parthenogenesis (Ghag, et al., 2014), making it extremely difficult to develop new disease‐resistant bananas via cross‐breeding (Czislowski et al., 2018). In recent years, host‐induced gene silencing (HIGS) has increasingly become one of the most practical technologies for generating new disease‐resistant crop varieties thanks to its high specificity and efficiency in silencing pathogen‐derived genes (Qi et al., 2018; Zhang et al., 2016).

Fruit ripening is the last phase of fruit growth and development. The initiation and progression of fruit ripening are highly modulated by a plethora of key genes, such as transcription factor (TF) genes. The WRKY gene family is a large group of TFs that play important roles in various cellular processes; nevertheless, the role of WRKY TF on fruit ripening remains enigmatic. Here, we report that a banana WRKY TF, MaWRKY49 functions in ethylene-induced fruit ripening by modulating the expression of fruit softening-related genes. We found that the expression of MaWRKY49 is highly induced by ethephon and inhibited by 1-methylcyclopropene, which is synchronous with the ripening process. Moreover, based on transcriptome data on fruit ripening, two pectate lyase (PL) genes that are involved in fruit softening were determined, and their expression pattern is also consistent with the fruit ripening process. Yeast one-hybrid and dual-luciferase assay confirmed that MaWRKY49 activated the transcription of two PL genes. In addition, transient overexpression of MaWRKY49 in banana fruits can apparently accelerate fruit ripening processs. Taken together, our findings indicate that MaWRKY49 acts as a potential modulator of fruit ripening by direct regulation of PL expression. This work contributes to developing the technology for improving the shelf-life of banana fruit.

Background: Banana plant height is an important trait for horticultural practices and semi-dwarf cultivars show better resistance to damages by wind and rain. However, the molecular mechanisms controlling the pseudostem height remain poorly understood. Herein, we studied the molecular changes in the pseudostem of a semi-dwarf banana mutant Aifen No. 1 (Musa spp. Pisang Awak sub-group ABB) as compared to its wild-type dwarf cultivar using a combined transcriptome and metabolome approach. Results: A total of 127 differentially expressed genes and 48 differentially accumulated metabolites were detected between the mutant and its wild type. Metabolites belonging to amino acid and its derivatives, flavonoids, lignans, coumarins, organic acids, and phenolic acids were up-regulated in the mutant. The transcriptome analysis showed the differential regulation of genes related to the gibberellin pathway, auxin transport, cell elongation, and cell wall modification. Based on the regulation of gibberellin and associated pathway-related genes, we discussed the involvement of gibberellins in pseudostem elongation in the mutant banana. Genes and metabolites associated with cell wall were explored and their involvement in cell extension is discussed. Conclusions: The results suggest that gibberellins and associated pathways are possibly developing the observed semi-dwarf pseudostem phenotype together with cell elongation and cell wall modification. The findings increase the understanding of the mechanisms underlying banana stem height and provide new clues for further dissection of specific gene functions.