Abstract

SQUAMOSA PROMOTER BINDING PROTEIN-LIKE(SPL) genes, as unique plant transcription factors, play important roles in plant developmental regulation and stress response adaptation. Although mulberry is a commercially valuable tree species, there have been few systematic studies onSPLgenes. In this work, we identified 15 full-lengthSPLgenes in the mulberry genome, which were distributed on 4Morus notabilischromosomes. Phylogenetic analysis clustered theSPLgenes from five plants (Malus × domestica Borkh,Populus trichocarpa,M. notabilis,Arabidopsis thaliana, andOryza sativa) into five groups. Two zinc fingers (Zn1 and Zn2) were found in the conserved SBP domain in all of theMnSPLs. Comparative analyses of gene structures and conserved motifs revealed the conservation ofMnSPLswithin a group, whereas there were significant structure differences among groups. Gene quantitative analysis showed that the expression ofMnSPLshad tissue specificity, andMnSPLshad much higher expression levels in older mulberry leaves. Furthermore, transcriptome data showed that the expression levels ofMnSPL7andMnSPL14were significantly increased under silkworm herbivory. Molecular experiments revealed thatMnSPL7responded to herbivory treatment through promoting the transcription ofMnTT2L2and further upregulating the expression levels of catechin synthesis genes (F3′H,DFR, andLAR).Keywords:mulberry;SPLs;phylogenetic analysis;silkworm herbivory;MnSPL7/MnTT2L2module