Genetical genomics of Populus leaf shape variation

Area of Science:

• Plant genetics
• Molecular biology
• Evolutionary biology

Background:

• Leaf morphology exhibits extensive variation across plant species, influenced by genetic factors.
• While mutagenesis screens reveal molecular mechanisms, the role of natural variation in these genes for leaf shape diversity remains unclear.
• Quantitative trait locus (QTL) analysis suggests polygenic control over leaf shape, indicating that mutagenesis-derived loci explain only a portion of natural variation.

Purpose of the Study:

• To identify genetic factors controlling leaf shape in a poplar pedigree using a genetical genomics approach.
• To investigate the molecular mechanisms underlying natural variation in leaf morphology within the Populus genus.

Main Methods:

• Utilized a poplar interspecific pseudo-backcross pedigree for genetical genomics analysis.
• Combined quantitative trait locus (QTL) discovery with transcriptome analysis of expanding leaf tissues.
• Employed Brefeldin A (BFA) to disrupt vesicular trafficking and assess its impact on leaf morphology.

Main Results:

• A stable major QTL associated with leaf lamina width and length:width ratio was identified.
• Transcriptome analysis pinpointed ADP-ribosylation factor (ARF) GTPase (PtARF1) as a candidate gene regulating leaf morphology.
• Pharmacological disruption of ARF GTPase function with BFA altered leaf lateral growth, implicating vesicular trafficking in leaf shape determination.

Conclusions:

• Results support a model where PtARF1 influences leaf expansion by modulating endocytosis-mediated PIN protein localization and lateral auxin flux.
• ARF proteins are crucial for controlling auxin efflux carrier localization, establishing auxin gradients, and apical-basal cell polarity.
• Evolution of differential cellular polarity is a significant factor in the observed leaf morphological variation within Populus subgenera.