AUTHOR=Gai Ying-Ping , Zhao Ya-Nan , Zhao Huai-Ning , Yuan Chuan-Zhong , Yuan Shuo-Shuo , Li Shuo , Zhu Bing-Sen , Ji Xian-Ling 

TITLE=The Latex Protein MLX56 from Mulberry (Morus multicaulis) Protects Plants against Insect Pests and Pathogens

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01475

DOI=10.3389/fpls.2017.01475

ISSN=1664-462X

ABSTRACT=<p>Biotic stresses are major constraints limiting the leaf quality and productivity of mulberry. MLX56 is a unique chitin-binding protein isolated from Shin-Ichinose (<italic>Morus alba</italic>) latex that displays toxicity against lepidopteran caterpillars. In this study, the full-length cDNA encoding MLX56 was isolated from Husang 32 (<italic>M. multicaulis</italic>) and designated <italic>HMLX56</italic>. Amino acid sequence analysis and protein modeling of three MLX56 proteins showed that they were highly conserved among <italic>Morus</italic> species. Tissue expression pattern analysis showed that the <italic>HMLX56</italic> gene was strongly expressed in mulberry bark and leaves but only slightly expressed in fruits. In addition, analysis of GUS expression indicated that the promoter of <italic>HMLX56</italic> showed higher transcriptional activity along the vascular strands, and its activity can be regulated by various environmental factors. Like the MLX56 protein from <italic>M. alba</italic>, the HMLX56 protein showed toxicity to <italic>Plutella xylostella</italic>. Moreover, when the <italic>HMLX56</italic> gene was ectopically expressed in Arabidopsis, the transgenic plants showed enhanced resistance to aphids, the fungal pathogen <italic>Botrytis cinerea</italic> and the bacterial pathogen <italic>Pseudomonas syringae</italic> pv. tomato DC3000. Our data suggest that the HMLX56 protein has a lectin-like molecular structure consisting of two hevein-like chitin-binding domains which provide not only chitin-binding activities but also other mechanisms of defense. The information provided here improves our understanding of the potential functions and defense mechanisms of MLX56 proteins, enabling in-depth functional analysis of latex exudates and perhaps facilitating mulberry genetic improvement in the future.</p>