Genome-Wide Analysis of the Polygalacturonase Gene Family in Macadamia and Identification of Members Involved in Fruit Abscission

Area of Science:

• Plant Biology
• Genomics
• Agricultural Science

Background:

• Severe physiological fruit abscission limits macadamia yield potential.
• Polygalacturonase (PG) enzymes are critical for pectin degradation and fruit abscission, but their roles in macadamia are unclear.

Purpose of the Study:

• To identify and characterize the polygalacturonase (PG) gene family in macadamia.
• To investigate the role of specific PG genes in macadamia fruit abscission.

Main Methods:

• Genome-wide identification and phylogenetic analysis of 56 PG genes (MiPGs) in macadamia.
• Analysis of MiPG gene structure, promoter regions, and expression patterns in fruit abscission zones.
• Functional validation of MiPG37 using transient overexpression in lily petals.

Main Results:

• 56 MiPG genes were identified, unevenly distributed across chromosomes and clustered into seven clades.
• Promoter analysis revealed light-, phytohormone-, and stress-responsive cis-elements in MiPG genes.
• Eight MiPG genes showed high expression in the abscission zone, with MiPG9, MiPG37, and MiPG53 upregulated during induced abscission.
• Overexpression of MiPG37 induced premature abscission in lily petals.

Conclusions:

• This study provides a comprehensive characterization of the macadamia PG gene family.
• Identified key MiPG genes, particularly MiPG37, play a pivotal role in macadamia fruit abscission.
• These findings offer candidate genes for genetic manipulation to enhance macadamia fruit retention and yield.