A research team has identified MaLBD50 as a key positive regulator of banana ripening that accelerates starch breakdown by directly activating the β-amylase gene MaBMY1. Increasing MaLBD50 expression hastened ripening and reduced pulp starch, whereas silencing it delayed ripening and preserved starch. The discovery clarifies how bananas convert stored starch into sugars and identifies a promising molecular target for breeding fruit with adjustable ripening rates, improved postharvest quality, and potentially longer shelf life.
Bananas (Musa spp.) are among the world's most widely traded fruits and an important staple food in many regions. As climacteric fruits ripen, starch is rapidly converted into soluble sugars while the pulp softens and changes in flavor, aroma, and color. Researchers have identified several transcription factors that activate or suppress genes involved in starch degradation, but the regulatory network remains incomplete. Lateral organ boundaries domain (LBD) proteins control diverse aspects of plant growth and metabolism, yet their contribution to banana ripening—and the size and evolutionary characteristics of the banana LBD family—has remained poorly understood.
A study (DOI: 10.48130/tp-0026-0026 ) published in Tropical Plants on 17 June 2026 by Zhuo Chen's team, Fujian Agriculture and Forestry University, reports that MaLBD50 drives ripening by activating MaBMY1 and promoting starch hydrolysis.
The researchers first searched the Musa acuminata genome and identified 77 LBD transcription factors distributed across all 11 chromosomes. Phylogenetic and synteny analyses compared these proteins with LBD family members in Arabidopsis thaliana and rice, revealing stronger conservation between banana and rice. The team then examined RNA-sequencing and DNase I hypersensitive-site sequencing data from four stages of banana development and ripening. Nine MaLBD genes were expressed more strongly in fully ripe fruit, while four—MaLBD4, MaLBD23, MaLBD24, and MaLBD50—also displayed accessible promoter chromatin and were selected as candidate ripening regulators. Functional tests using Agrobacterium-mediated transient transformation showed that overexpressing MaLBD50 accelerated banana ripening, whereas RNA interference-mediated silencing delayed it. MaLBD50 expression increased approximately 3.3-fold in overexpression tissues. Correspondingly, starch content fell by 32.6% compared with the control, while silenced pulp retained 9.9% more starch, demonstrating a direct relationship between MaLBD50 activity and starch hydrolysis. To map the broader regulatory network, the researchers integrated DNA affinity purification sequencing, DNase sequencing, and RNA sequencing. They identified 7,813 high-confidence candidate targets, with 28.39% of binding peaks located in promoter regions. The analysis highlighted several ripening-related genes, including MaAMY3, associated with starch breakdown; MaEXPA8, involved in cell-wall loosening; and MaINV1, which participates in sugar metabolism. A β-amylase gene, MaBMY1, emerged as a particularly important target. DNA affinity purification–quantitative polymerase chain reaction confirmed enrichment of MaLBD50 at its accessible promoter region. Yeast one-hybrid experiments demonstrated direct binding, while dual-luciferase assays in tobacco leaves showed that MaLBD50 strongly activated MaBMY1 transcription. Together, these results establish a direct regulatory pathway linking a specific transcription factor to starch degradation during banana ripening.
The study expands the known functions of plant LBD transcription factors and provides a molecular framework for managing banana ripening. Precision editing or fine-tuning of MaLBD50 could eventually help delay ripening during transport or accelerate it before sale, although effects on softening, flavor, and other ripening pathways require further evaluation. Tissue-specific promoters, promoter editing, and naturally occurring genetic variants may offer safer approaches than completely disabling this broadly acting regulator. Overall, the MaLBD50–MaBMY1 module provides both a mechanistic explanation for starch-to-sugar conversion and a potential breeding target for high-quality bananas with improved postharvest performance.
