Genome-Wide Analysis of SPL Gene Family and Functional Identification of JrSPL02 Gene in the Early Flowering of Walnut

SPL transcription factors affect plant growth and development, including blooming and photoperiod control. The investigation began with transcriptome data screening of 28 JrSPL genes in walnut (Junglans regia L.) ‘Wen185’. These genes were discovered on all chromosomes except 6 and 15. Phylogenetic study divides the 28 JrSPL genes into five groupings. The biggest cluster, cluster IV, has 12 JrSPL genes. The expression of JrSPL genes in different tissues was investigated by qRT-PCR. JrSPL02 gene expression was greater in walnut female and male flower tissues than other genes. Subcellular localization has shown the JrSPL02 gene resides in the nucleus. Jre-miR156 may target JrSPL02’s 3′-UTR region, according to miRNA sequencing, RACE, and BiFC studies. Arabidopsis plants expressing the JrSPL02 gene flowered 3 days faster than the wild type, according to phenotypic observation. Transgenic lines had more stem branches and siliques than the control group but fewer rosette leaves. In summary, this study functionally analyses the metamorphosis of the miR156-SPL module during the blooming stage and the underlying mechanisms that govern early fruiting in early-fruiting walnuts in Xinjiang.