LcMYB306 regulates litchi fruit water loss and browning by inhibiting the expression of LcPIP2;4

Xiaoxu Li, Fang Li, Guo Wang, Shujun Wang, Xueren Cao, Ya Wu, Huanling Li, Jiabao Wang

Horticulture Research; 21 November 2025; uhaf322, https://doi.org/10.1093/hr/uhaf322

Abstract

Pericarp browning of postharvest litchi is a significant obstacle to the industry's high-quality development. Water loss from the pericarp is a key factor triggering browning, but the regulatory mechanism of water metabolism and its relationship with browning remain unclear. In this study, we found that aquaporin activity inhibitors (HgCl₂) can delay both water loss and browning in litchi. LcPIP2;4, a PIP family member exhibiting high expression in the litchi pericarp and the greatest water transport activity, is significantly downregulated during water loss and browning. Further analysis revealed that HgCl₂ suppresses both the expression and water transport activity of LcPIP2;4, indicating a close association with the observed browning phenotype. By constructing transient overexpression fruits and transgenic callus tissues of LcPIP2;4 and measuring the water loss rate and browning index, we confirmed that LcPIP2;4 positively regulates water loss and browning in litchi. Through weighted gene co-expression network, LcPIP2;4 promoter sequence and qRT-PCR analysis, we identified 10 potential interacting transcription factors. Yeast one-hybrid, dual-luciferase reporter assay, chromatin immunoprecipitation analysis and electrophoretic mobility shift assay confirmed that LcMYB306 specifically binds to the LcPIP2;4 promoter. In LcMYB306 overexpressing fruits and embryogenic callus, LcPIP2;4 expression was suppressed, resulting in delayed water loss and browning. In contrast, in CRISPR/Cas9-edited LcMYB306 callus, LcPIP2;4 expression was upregulated, and water loss and browning were accelerated, confirming that LcMYB306 negatively regulates this process. This study demonstrates that LcMYB306 delays postharvest water loss and browning in litchi by repressing LcPIP2;4 transcriptionally expression. It provides a theoretical foundation and key target gene for developing litchi varieties resistant to browning.

See https://academic.oup.com/hr/advance-article/doi/10.1093/hr/uhaf322/8339624?login=false

Figure 1:

Changes in browning and water loss in litchi following 200 μM HgCl2 treatment over a 6-day 123 storage period at room temperature. (A) Phenotypic observations, (B) chromatism value, (C) browning 124 index, (D) water loss, and (E) correlation analysis of browning index and water loss of litchi pericarps after 125 HgCl2 treatment over 6 days of storage. Means and standard errors were calculated from three biological 126 replicates, each treatment consisting of 30 fruits. Asterisks (*, **, and ***) indicate significant differences at 127 P < 0.05, P < 0.01, and P < 0.001, respectively (t-test)