Plant height is an important and valuable agronomic trait associated with yield and resistance to abiotic and biotic stresses. Dwarfism has positive effects on plant development and field management, especially for tall monocotyledon banana (Musa spp.). However, several key genes and their regulation mechanism of controlling plant height during banana development are unclear. In the present study, the popular cultivar ‘Brazilian banana’ (‘BX’) and its dwarf mutant (‘RK’) were selected to identify plant height-related genes by comparing the phenotypic and transcriptomic data. Banana seedlings with 3–4 leaves were planted in the greenhouse and field. We found that the third and fourth weeks are the key period of plant height development of the selected cultivars. A total of 4563 and 10507 differentially expressed genes (DEGs) were identified in the third and fourth weeks, respectively. Twenty modules were produced by the weighted gene co-expression network analysis (WGCNA). Eight modules were positively correlated with the plant height, and twelve other modules were negatively correlated. Combining with the analysis of DEGs and WGCNA, 13 genes in the signaling pathway of gibberellic acid (GA) and 7 genes in the signaling pathway of indole acetic acid (IAA) were identified. Hub genes related to plant height development were obtained in light of the significantly different expression levels (|log2FC| ≥ 1) at the critical stages. Moreover, GA3 treatment significantly induced the transcription expressions of the selected candidate genes, suggesting that GA signaling could play a key role in plant height development of banana. It provides an important gene resource for the regulation mechanism of banana plant development and assisted breeding of ideal plant architecture.

Nitrogen is a crucial element for the growth and development of plants, directly affecting crop growth and yield. To investigate the physiological and molecular mechanism of nitrogen-deficiency stress, we conducted an investigation into the effects of different nitrogen levels on the growth, photosynthetic characteristics, and gene transcription levels of banana seedlings. Compared with the control group with normal nitrogen levels (NN), the height of plants receiving Reduced-N (NR), Low-N (LN), and N-Free (NF) treatments was decreased by 0.45 cm, 2.5 cm, and 3.25 cm, respectively. Their dry weight was reduced by 1.63 g, 2.99 g, and 2.88 g, respectively. Conversely, the dry weight of the underground plant part in the LN and NF treatment groups exhibited an increase of 0.13 g and 0.16 g, respectively. Regarding photosynthetic characteristics, the Specialty Products Agricultural Division (SPAD) values of the NR, LN, and NF treatments showed reductions of 15.5%, 30.4%, and 35.9%, respectively, compared with those of the control treatments. The values of maximum photosynthetic efficiency (Fv/Fm), actual photosynthetic efficiency (Y(Ⅱ)), and relative electron transfer (ETR) of the banana seedlings decreased to different degrees after NR, LN, and NF treatment, and their values were positively correlated with N levels. Gene transcription analysis showed that N transport-related proteins, including NRT1.7, NRT2.3a, NRT2.3b, and NRT2.5, were significantly up-regulated to increase the nitrogen absorption capacity of plant roots. On the other hand, various transcription factors including GRAS, MYB, and WRKY were notably up-regulated, facilitating root growth and the expanding root absorption area, thereby enhancing nitrogen uptake. Furthermore, genes associated with endogenous hormone metabolic pathways such as gibberellin (GA), strigolactone (SL), and brassinosteroids (BR) were activated in banana plants subjected to low nitrogen stress, enhancing the plant’s ability to adapt to nitrogen-deficient conditions. These findings offer valuable insights into understanding the transcriptional regulatory mechanisms governing banana responses to low nitrogen stress and breeding new varieties with improved nutrient utilization.

The TGA (TGACG motif-binding factor) transcription factors are integral to root growth and development, and are pivotal in mediating plant responses to abiotic stresses. Nonetheless, their role in the nutrient absorption processes of banana plants has not been extensively investigated. This research conducted a comprehensive analysis of the MaTGA gene family, emphasizing their physicochemical characteristics, phylogenetic relationships, gene duplication events, promoter cis-regulatory elements and protein interaction networks. Furthermore, this study investigated the expression patterns of MaTGA family members under varying nitrogen conditions. A total of 18 MaTGA members were identified within the banana genome, each encoding proteins characterized by the presence of bZIP and DOG domains. These genes exhibited an uneven distribution across eight chromosomes. Phylogenetic analysis further classified the MaTGA family into four distinct subgroups (I–IV), consisting of three, seven, three, and five members, respectively. An analysis of promoter cis-elements indicated that over 50% of the MaTGA gene family members contain hormone-responsive elements associated with abscisic acid (ABRE), ethylene (ERE), and salicylic acid (SARE), in addition to stress-responsive elements related to drought (MBS) and low temperature (LTR). Regarding gene expression, MaTGA7, MaTGA8, and MaTGA15 exhibited significantly elevated expression levels in the leaves and roots relative to other tissues. Under varying nitrogen conditions, 13 members, including MaTGA7 and MaTGA8, demonstrated the highest expression levels under reduced nitrogen (70%) treatment, followed by low nitrogen (20%) conditions, and the lowest expression levels were observed under nitrogen-deficient conditions. These findings imply that MaTGA genes may play crucial roles in enhancing nitrogen use efficiency. Protein interaction predictions suggest that MaTGA7, MaTGA8, and MaTGA15 may interact with nitrogen-related proteins, including Nitrate Transporter 2 (NRT2.1 and NRT2.2), NIN-Like Protein 7 (NLP7), and Nitrate Transporter 1.1 (NPF6.3). In summary, MaTGA7, MaTGA8, and MaTGA15 are likely involved in the processes of nitrogen absorption and utilization in bananas. The present findings establish a basis for subsequent investigations into the functional roles of MaTGA genes in augmenting nutrient use efficiency and mediating responses to abiotic stresses in banana plants.

Banana wilt caused by Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) is a devastating fungal disease. Biocontrol strategies owned immense potential in inhibiting the spread of Foc TR4. Here, thirty actinobacteria were isolated from soils and screened for their antagonistic activity against Foc TR4. Strain SCA4-21T exhibited broad-spectrum antifungal activity against nine phytopathogenic fungi including Foc TR4. The strain was identified as the genus Streptomyces according to phenotypic characteristics and 16S rRNA gene phylogenetic analysis. Multi-locus sequence analysis based on five house-keeping gene alleles (atpD, gyrB, recA, rpoB, and trpB) revealed that strain SCA4-21T clustered into S. hygroscopicus subsp. hygroscopicus NBRC 13472T with 100% of bootstrap value. Average nucleotide identity and dDDH were 98.49% and 44.30% above the threshold of novel species. Hence, strain SCA 4-21T represented a novel species within the genus Streptomyces, named as Streptomyces luomodiensis sp. nov.. The type strain is SCA4-21T (=GDMCC4.340T= JCM36555T). By the CAZymes analysis, 348 carbohydrate-active enzymes were detected, including 15 chitinases and 8 β-1,3-glucanases. The fermentation broth of strain SCA4-21T showed high activities of chitinase and β-1,3-glucanase, contributing to the antifungal activity. Our results showed an innovative potential biocontrol agent for managing plant fungal diseases, specifically banana fusarium wilt.