AUTHOR=Fu Yaru , Li Feiran , Mu Shuaicheng , Jiang Libo , Ye Meixia , Wu Rongling 

TITLE=Heterophylly Quantitative Trait Loci Respond to Salt Stress in the Desert Tree Populus euphratica

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.692494

DOI=10.3389/fpls.2021.692494

ISSN=1664-462X

ABSTRACT=<p>Heterophylly, or leaf morphological changes along plant shoot axes, is an important indicator of plant eco-adaptation to heterogeneous microenvironments. Despite extensive studies on the genetic control of leaf shape, the genetic architecture of heterophylly remains elusive. To identify genes related to heterophylly and their associations with plant saline tolerance, we conducted a leaf shape mapping experiment using leaves from a natural population of <italic>Populus euphratica</italic>. We included 106 genotypes grown under salt stress and salt-free (control) conditions using clonal seedling replicates. We developed a shape tracking method to monitor and analyze the leaf shape using principal component (PC) analysis. PC1 explained 42.18% of the shape variation, indicating that shape variation is mainly determined by the leaf length. Using leaf length along shoot axes as a dynamic trait, we implemented a functional mapping-assisted genome-wide association study (GWAS) for heterophylly. We identified 171 and 134 significant quantitative trait loci (QTLs) in control and stressed plants, respectively, which were annotated as candidate genes for stress resistance, auxin, shape, and disease resistance. Functions of the stress resistance genes <italic>ABSCISIC ACIS-INSENSITIVE 5-like</italic> (<italic>ABI5</italic>), <italic>WRKY72</italic>, and <italic>MAPK3</italic> were found to be related to many tolerance responses. The detection of <italic>AUXIN RESPONSE FACTOR17-LIKE</italic> (<italic>ARF17</italic>) suggests a balance between auxin-regulated leaf growth and stress resistance within the genome, which led to the development of heterophylly <italic>via</italic> evolution. Differentially expressed genes between control and stressed plants included several factors with similar functions affecting stress-mediated heterophylly, such as the stress-related genes <italic>ABC transporter C family member 2</italic> (<italic>ABCC2</italic>) and <italic>ABC transporter F family member</italic> (<italic>ABCF</italic>), and the stomata-regulating and reactive oxygen species (ROS) signaling gene <italic>RESPIRATORY BURST OXIDASE HOMOLOG</italic> (<italic>RBOH</italic>). A comparison of the genetic architecture of control and salt-stressed plants revealed a potential link between heterophylly and saline tolerance in <italic>P. euphratica</italic>, which will provide new avenues for research on saline resistance-related genetic mechanisms.</p>