PbrmiR397a regulates lignification during stone cell development in pear fruit

Area of Science:

• Plant Molecular Biology
• Agricultural Science
• Biochemistry

Background:

• Lignified stone cells negatively impact fruit quality, necessitating genetic strategies to control their development.
• The precise molecular mechanisms governing lignification in fruit stone cells remain largely unelucidated.
• Understanding these mechanisms is crucial for developing methods to enhance fruit characteristics.

Purpose of the Study:

• To investigate the role of microRNA (miR) miR397a in regulating lignin biosynthesis and stone cell formation in fruit.
• To identify molecular targets and genetic factors influencing miR397a activity in relation to fruit quality.

Main Methods:

• Transient overexpression of Chinese pear miR397a (PbrmiR397a) and silencing of laccase (LAC) genes in pear fruit.
• Analysis of a single nucleotide polymorphism (SNP) in the PbrmiR397a promoter across 60 pear varieties.
• Cell-based assays to confirm the function of the SNP and its response to salicylic acid.
• Stable overexpression of PbrmiR397a in transgenic tobacco plants to assess effects on lignin and cell wall structure.

Main Results:

• Overexpression of PbrmiR397a and LAC gene silencing significantly reduced lignin content and stone cell numbers in pear fruit.
• A promoter SNP in PbrmiR397a was associated with reduced fruit lignin and created a salicylic acid-responsive element.
• Transgenic tobacco plants overexpressing PbrmiR397a exhibited decreased LAC gene expression, lower lignin content, and altered vessel element structure.

Conclusions:

• miR397a acts as a negative regulator of lignin biosynthesis by targeting LAC genes in fruit.
• A naturally occurring SNP in the PbrmiR397a promoter influences lignin levels and offers a potential marker for breeding.
• This research provides valuable molecular insights for genetic improvement of fruit quality by controlling stone cell development.