The YUCCA enzymes sit at a critical bottleneck in plant hormone metabolism. They are flavin monooxygenases that function as the rate-limiting step in the indole-3-pyruvic acid, or IPA, pathway, converting IPA into indole-3-acetic acid, the principal naturally occurring auxin known as IAA. Because auxin cannot be synthesized efficiently without them, YUCCA genes effectively control how much of this growth-promoting signal a plant can produce at any given moment. Since the first YUCCA genes were characterized in Arabidopsis two decades ago, versions of the family have been identified in rice, apple, soybean, oilseed rape, peach and many other species, and they have repeatedly been linked to organ formation, vascular development, embryogenesis and stress responses. What remained unknown was how this family looks in mango and what its members actually do.

To answer that question, the Guangxi team mined the published mango genome and identified twelve MiYUCCA genes. Phylogenetic analysis, which compares protein sequences to reconstruct evolutionary relationships, sorted the twelve members into five distinct categories, mirroring the subfamily structure seen in other plants. The researchers then scanned the promoter regions upstream of each gene for cis-acting regulatory elements, the short DNA motifs that transcription factors recognize. This analysis revealed a dense array of hormone-responsive elements alongside motifs associated with abiotic stress, suggesting that mango YUCCA genes are positioned to respond to both developmental cues and environmental challenges. Such promoter architecture provides a roadmap for guessing, and then testing, when and where each gene might act.

Expression profiling across mango fruit development delivered the first major clue. Most of the MiYUCCA genes showed their highest abundance during the earliest stages of fruit growth, after which their expression declined sharply or switched off entirely as the fruit matured. This pattern fits neatly with what is known about auxin’s role in early fruit set, when cell division is rapid and high auxin levels help establish the tissues that will later expand and ripen. It also echoes findings in peach, strawberry and grape, where specific YUCCA genes have been tied to auxin biosynthesis during fruit development and ripening. The message from the expression data was clear: the mango YUCCA family is most active precisely when the fruit is being founded, not when it is filling out.

From the twelve candidates, the team selected two closely related members, MiYUCCA10A and MiYUCCA10B, for functional verification. Using Agrobacterium-mediated transformation, they generated transgenic Arabidopsis plants overexpressing each gene, and then extended the work into tomato, a crop species with a very different growth habit and fruit biology. The results were striking. Transgenic plants of both species flowered significantly earlier than their wild-type counterparts, and measurements confirmed that the engineered plants contained elevated levels of IAA, consistent with the introduced YUCCA enzymes actively boosting auxin biosynthesis. Early flowering is a trait of enormous practical interest, because many fruit trees, mango included, have long juvenile phases that delay breeding programs and orchard returns by years.

The stress-resistance results were equally compelling. When the transgenic Arabidopsis and tomato lines were subjected to salt and drought treatments, they tolerated the challenges markedly better than control plants, surviving and growing under conditions that stunted the wild types. This dual function, promoting both development and stress tolerance, is consistent with a growing body of literature showing that auxin is deeply intertwined with abiotic stress signaling. Previous work has shown, for example, that overexpressing Arabidopsis YUCCA6 in poplar and potato confers auxin-overproduction phenotypes along with enhanced tolerance to water deficit, and that activating YUCCA7 in Arabidopsis improves drought resistance. The mango genes now join this list, and they do so in a horticulturally significant species.

But the story was not one of unalloyed benefits. The overexpression lines carried clear reproductive costs. In both transgenic Arabidopsis and tomato, the number of seeds produced was significantly reduced. Arabidopsis pod length was unaffected, but tomato fruit size dropped markedly in the engineered lines. These trade-offs matter. They illustrate a principle that plant biologists have learned repeatedly: hormones as central as auxin cannot simply be cranked up without consequences, because the same signal that accelerates flowering and hardens plants against stress also participates in seed set and fruit expansion. For any future attempt to deploy MiYUCCA10 genes in crop improvement, the challenge will be to capture the flowering and stress benefits while avoiding penalties on yield and fruit quality, perhaps through tissue-specific or inducible promoters rather than constitutive overexpression.

Perhaps the most intriguing mechanistic discovery came from protein interaction experiments. Using yeast two-hybrid assays and bimolecular fluorescence complementation, a technique that reconstitutes a fluorescent protein only when two candidate partners physically meet inside plant cells, the researchers showed that MiYUCCA10A and MiYUCCA10B interact with five mango proteins: MiSVP1, MiSVP2, MiSVP3, MiSVP4 and MiSVP5, all homologs of SHORT VEGETATIVE PHASE, as well as MiFLC, the mango version of FLOWERING LOCUS C. SVP and FLC are central repressors of the floral transition, the genetic switch that converts a vegetative shoot apex into an inflorescence. In Arabidopsis, FLC holds flowering in check until winter cold or other cues remove it, and SVP proteins act with FLC in repressive complexes. Finding auxin biosynthesis enzymes physically associated with these flowering-time repressors suggests a direct biochemical link between hormone production and the floral transition machinery, hinting that MiYUCCA10 proteins may do more than simply raise auxin levels; they may participate in regulatory complexes that decide when a plant commits to flowering.

The study is part of a broader research program at Guangxi University that has systematically dissected mango flowering genes, including earlier work on the CONSTANS family, the SPL transcription factors and the auxin response factor MiARF18A, each of which also produced early-flowering phenotypes when tested in transgenic Arabidopsis. Together these studies are assembling a molecular wiring diagram of how a tropical fruit tree decides to flower, a process that in orchards is governed by season, temperature and tree age. The work was supported by the National Natural Science Foundation of China and Guangxi science and technology funding programs, reflecting regional investment in one of the province’s signature crops.

For the wider research community, the mango YUCCA study delivers three things at once: a complete genomic inventory of a key auxin biosynthesis family in a major tropical fruit, functional proof that two of its members can reprogram flowering time and stress responses in heterologous species, and a physical interaction map connecting auxin synthesis to canonical flowering repressors. The trade-offs observed in fruit size and seed number are a sober reminder that hormone engineering demands precision, but they also sharpen the questions that future experiments must answer. If researchers can find ways to deploy MiYUCCA10A/B activity only where and when it helps, the prospect of mango trees that flower sooner, shrug off drought and salinity, and still bear full-sized fruit moves from speculation toward genuine breeding strategy. In the meantime, the humble mango has offered science a vivid demonstration that a single pair of enzymes can sit at the crossroads of flowering, stress and fruit development all at once.

Subject of Research: Functional characterization of the mango YUCCA auxin biosynthesis gene family and the effects of MiYUCCA10A/B overexpression on flowering, stress tolerance and fruit development

Article Title: Genome-wide analysis of the mango YUCCA family and overexpression of MiYUCCA10A/B confers early flowering and stress tolerance in transgenic Arabidopsis and tomato

Article References: He, Z., Hu, W., Qin, L., Huang, C., Li, R., Xu, F., Xie, F., Luo, C., & He, X. (2026). Genome-wide analysis of the mango YUCCA family and overexpression of MiYUCCA10A/B confers early flowering and stress tolerance in transgenic Arabidopsis and tomato. Plant Cell Reports, 45(10), Article 304. https://doi.org/10.1007/s00299-026-03981-9

Image Credits: AI Generated

DOI: 10.1007/s00299-026-03981-9

Keywords: mango, YUCCA, auxin, IAA biosynthesis, early flowering, salt tolerance, drought tolerance, transgenic plants, Arabidopsis, tomato, MiSVP, FLC