Comparative gene expression analysis reveals that multiple mechanisms regulate the weeping trait in Prunus mume

Abstract

Prunus mume (also known as Mei) is an important ornamental plant that is popular with Asians. The weeping trait in P. mume has attracted the attention of researchers for its high ornamental value. However, the formation of the weeping trait of woody plants is a complex process and the molecular basis of weeping stem development is unclear. Here, the morphological and histochemical characteristics and transcriptome profiles of upright and weeping stems from P. mume were studied. Significant alterations in the histochemical characteristics of upright and weeping stems were observed, and the absence of phloem fibres and less xylem in weeping stems might be responsible for their inability to resist gravity and to grow downward. Transcriptome analysis showed that differentially expressed genes (DEGs) were enriched in phenylpropanoid biosynthesis and phytohormone signal transduction pathways. To investigate the differential responses to hormones, upright and weeping stems were treated with IAA (auxin) and GA3 (gibberellin A3), respectively, and the results revealed that weeping stems had a weaker IAA response ability and reduced upward bending angles than upright stems. On the contrary, weeping stems had increased upward bending angles than upright stems with GA3 treatment. Compared to upright stems, interestingly, DEGs associated with diterpenoid biosynthesis and phenylpropanoid biosynthesis were significantly enriched after being treated with IAA, and expression levels of genes associated with phenylpropanoid biosynthesis, ABC transporters, glycosylphosphatidylinositol (GPI)—anchor biosynthesis were altered after being treated with GA3 in weeping stems. Those results reveal that multiple molecular mechanisms regulate the formation of weeping trait in P. mume, which lays a theoretical foundation for the cultivation of new varieties.

Defying Gravity:WEEPpromotes negative gravitropism inPrunus persica(peach) shoots and roots by establishing asymmetric auxin gradients

“…This effect was not observed in weep peaches, where GA application did not alter the weeping phenotype (Hollender et al, 2018). Similar to Japanese cherry, weeping Japanese apricot (Prunus mume) trees have decreased xylem tissue width, and lack phloem fibers (Li et al, 2021b).…”

“…This pendulous growth habit, where branches bend or grow downward in the direction of gravity, exists in both gymnosperm and angiosperm lineages. The weeping trait has been mapped to single, but distinct, loci in multiple species, including Eastern redbud (Cercis canadensis), morning glory (Pharbitis nil), Japanese apricot (Prunus mume), and peach (Prunus persica) (Kitazawa et al, 2005;Hollender et al, 2018;Chen and Werner, 2021;Li et al, 2021b). Despite often being controlled by a single locus, the change to a pendulous growth habit leads to diverse alterations in plant anatomy and physiology-such as modifications in light interception, canopy density, and canopy size.…”