Identification of pectin acetylesterase genes in moso bamboo (Phyllostachys edulis) reveals PePAE6 involved in pectin accumulation of leaves

Abstract

As an indispensable polysaccharide, pectin profoundly affects various aspects of plant growth and development. Pectin acetylesterase (PAE) adjusts the acetylation level of pectin, thereby affecting the properties of pectin and cell walls, particularly in tissues such as leaves, where primary cell walls are predominant and rich in pectin. However, the PAE family in bamboo remains unknown. In the present study, ten PAE genes (PePAE1-PePAE10) were identified and characterized in moso bamboo (Phyllostachys edulis). All PePAEs possessed unique conserved domains and motifs of plant PAEs. The expression patterns of PePAEs varied across different tissues and developmental stages, indicating the sub-functionalization of these genes. Notably, the expression level of PePAE6 displayed the most remarkable change during leaf growth and was co-expressed with multiple transcription factors. Using various experimental approaches, we found that PeWRKY-1 and PeWRKY-2 negatively regulated PePAE6 by binding to its promoter. Knockdown of PeWRKY-1 or PeWRKY-2 inversely increased expression of PePAE6. While knockdown of PePAE6 resulted in increased acetylation levels and reduced galacturonic acid (GalA) content in moso bamboo leaves. Furthermore, overexpression of PePAE6 in rice indirectly enhanced vegetative growth and photosynthetic capacity, with a reduction in pectin acetylation levels and an increase in GalA. Additionally, an in vitro pectin acetylesterase activity assay confirmed that PePAE6 catalyzed pectin deacetylation, releasing acetic acid as a byproduct. These findings provide valuable insights into the basic characteristics of PAE in bamboo and reveal that PePAE6 is a functional gene involved in pectin accumulation, which could be helpful in genetic engineering in bamboo breeding.