Genome-Wide Identification and Expression Analysis of the Nucleotide-Binding Leucine-Rich Repeat Gene Families in
Xianbao Liu1, Huiqing Xu1, Boxun Li1
1Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Key Laboratory of Integrated Pest Management on Tropical Crops, Ministry of Agriculture, Key Laboratory for Monitoring and Control of Tropical Agricultural Pests, Haikou, Hainan, China.
Abstract:
Anthracnose, caused by Colletotrichum spp., significantly threatens rubber trees globally. The nucleotide-binding and leucine-rich repeat (NLR) protein family constitutes one of the largest and most widespread classes of plant immune receptors. However, the specific relationship between NLR genes and anthracnose resistance in rubber trees remains poorly understood. This study comprehensively identified all NLR family members in the reference genome of the wild rubber tree accession MT/VB/25A 57/8. From 39,340 annotated proteins, 253 were classified as NLRs, including 155 coiled-coil NLR (CNL) and 35 Toll/interleukin-1 receptor NLR (TNL) proteins. Conserved motifs were identified in both CNL and TNL proteins. Notably, TNL proteins had a higher occurrence of conserved motif 8 in C-terminal leucine-rich repeat domains than CNL proteins. Chromosomal mapping indicated that CNL and TNL protein-coding genes largely localized on chromosomes 1, 3, 8, 12, and 14. The observed NLR distribution and diversity likely resulted from tandem, ectopic, and segmental gene duplications, with tandem duplications being the most common. Comparative transcriptome and quantitative RT-PCR analyses revealed two specific CNL genes (LOC110667987 and LOC110668014) preferentially expressed in a resistant genotype upon infection by Colletotrichum siamense. Identification of these genes provides insight into the molecular mechanisms of anthracnose resistance and will facilitate the development of resistant rubber trees.
