A single amino acid substitution in MdLAZY1A dominantly impairs shoot gravitropism inMalus

Abstract

Plant architecture is one of the most important factors that determines crop yield potential and productivity. In apple (Malus), genetic improvement of tree architecture has been challenging due to a long juvenile phase and their growth as complex trees composed of a distinct scion and a rootstock. To better understand the genetic control of apple tree architecture, the dominant weeping growth phenotype was investigated. We report the identification of MdLAZY1A (MD13G1122400) as the genetic determinant underpinning the Weeping (W) locus that largely controls weeping growth in Malus. MdLAZY1A is one of the four paralogs in apple that are most closely related to AtLAZY1 involved in gravitropism in Arabidopsis. The weeping allele (MdLAZY1A-W) contains a single nucleotide mutation c.584T>C that leads to a leucine to proline (L195P) substitution within a predicted transmembrane domain that co-localizes with Region III, one of the five conserved regions in LAZY1-like proteins. Subcellular localization revealed that MdLAZY1A localizes to the plasma membrane and nucleus in plant cells. Over-expressing the weeping allele in apple cultivar Royal Gala (RG) with standard growth habit impaired its gravitropic response and altered the growth to weeping-like. Suppressing the standard allele (MdLAZY1A-S) by RNA interference (RNAi) in RG similarly changed the branch growth direction to downward. Overall, the L195P mutation in MdLAZY1A is genetically causal for weeping growth, underscoring not only the crucial roles of residue L195 and Region III in MdLAZY1A-mediated gravitropic response, but also a potential DNA base editing target for tree architecture improvement in Malus and other crops.

A haplotype-resolved chromosome-scale genome for Quercus rubra L. provides insights into the genetics of adaptive traits for red oak species

“…Branch angle is a key shoot architecture trait that may influence photosynthesis efficiency, tree canopy size, tree height, and wood quality ( Ehleringer and Werk 1986 ; Ezcurra et al 1991 ; Glenn et al 2015 ; Hill and Hollender 2019 ). IGTs have been found to play a role in tree architecture of peach, apple, poplar, and orange trees ( Dougherty et al 2023 ; Dutt et al 2022 ; Fladung 2021 ; Waite and Dardick 2021 ).…”