# GA4/GA7 Deficiency and Downregulated Ent-Kaurenoic Acid Oxidase Impair Seedless Mango Fruit Development

## TL;DR

Seedless mangoes often fail to develop properly due to low GA4/GA7 levels and reduced KAO gene activity, which can be improved with GA4+7 supplements.

## Contribution

The study identifies GA4/GA7 deficiency and downregulated KAO as key factors in poor seedless mango development and suggests GA4+7 as a more effective treatment than GA3.

## Key findings

- GA4 and GA7 levels are significantly lower in seedless mangoes during critical development stages.
- GA4+7 supplementation at 30 DAB improves fruit growth more effectively than GA3.
- The KAO gene (Mi05g23760.1) is strongly correlated with GA levels and is downregulated in underdeveloped seedless mangoes.

## Abstract

Seedless mangoes are desirable for fresh consumption and processing; however, they frequently exhibit poor fruit development and elevated abscission rates, necessitating applications of fruit regulators, though their physiological and molecular targets remain unclear. In this study, hormonal deficits and regulatory genes associated with mango fruit development were identified. Morphological observations showed that embryo-containing (EC) and embryo-absent (EA) fruits begin to diverge in development between 30 and 45 days after bloom (DAB). During this period, targeted metabolomics of gibberellins (GAs) detected nine GAs; four (GA20, GA34, GA4, GA7) behaved consistently across cultivars, with GA4 and GA7 showing the largest declines in EA fruit. Applying 50 mg/L GA3 or GA4+7 at 30 DAB increased fruit growth versus water, with GA4+7 having the greatest effect. Comparative transcriptomic analysis revealed 1476 shared DEGs that were enriched in hormone signaling pathways. Among 13 DEGs involved in GA biosynthesis, KAO (Mi05g23760.1) showed the strongest correlation with GA levels and was markedly downregulated in EA fruits. Together, these results indicate that deficiencies in GA4/GA7—potentially resulting from reduced KAO expression—contribute to impaired EA fruit development and that targeted GA4+7 supplementation may more effectively rescue growth than conventional GA3 treatments. These results provide mechanistic insights and practical guidance for hormone-based strategies to promote consistent development of seedless mangoes, thereby improving yield stability and supporting more sustainable production.