Intron Retention Fine-Tunes the Resistance of the Rice Mutant pls4 to Rice Sheath Blight(Rhizotonia solani AG I.1a)

OsPLS4 encodes aβ-ketoacyl carrier protein reductase(KAR).The role of OsPLS4 in rice sheath blight(Rhizoctonia solani)remains unclear.Our preliminary studies showed that premature leaf senescence mutants(pls4)were highly susceptive to sheath blight in the early stage of rice development.To explore the role of this gene in the development of rice sheath blight,the transcriptome profiles of the rice pls4 mutant and wild type were compared by RNA-seq.The results revealed 2,569 differentially expressed genes(DEGs).The down-regulated genes were significantly enriched in the defense response-related biological processes.These down-regulated genes included the chitinase genes and WRKY genes,which were significantly changed in pls4 mutants.Furthermore,467 genes induced significant alternative splicing(AS)events.Among them,intron retention(IR)affected gene expression levels and functions of the vitamin B6(VB6)metabolism pathway related to sheath blight.This result suggests that IR plays an important role in the sheath blight resistance of mutant pls4.Together,these results indicate that pls4 could be involved in the biological process of sheath blight via DEGs and the fine-tuning of IR.The present study provides a molecular basis for further investigation of the resistance of rice to sheath blight.

SUPEROXIDE DISMUTASE FAMILY GENES IN WATERMELON AND THEIR RESPONSES TO DIFFERENT ABIOTIC STRESSES

Superoxide dismutase(SOD)is an important enzyme in the antioxidant system of plants and plays a vital role in stress responses by maintaining the dynamic balance of reactive oxygen species(ROS)concentrations.Genome-wide analysis of the SOD gene family in various plant species has been conducted but little is known about this gene family in watermelon(Citrullus lanatus).Here,eight SOD genes were identified in the watermelon genome and are designated Cl CSD1-5,Cl FSD1-2 and Cl MSD according to their metal cofactors.Phylogenetic analysis shows that SOD proteins from various plant species can be classified into five groups and members in the same group possess the same metal cofactor and similar subcellular localizations.Expression analysis of the Cl SOD genes indicates that they had tissue-specific expression patterns with high expression in different tissues including the leaves,flowers and fruits.In addition,the expression of Cl SOD genes differed appreciably under salinity,drought and abscisic acid(ABA)treatments,indicating that they may be involved in ROS scavenging under different abiotic stresses via an ABA-dependent signaling pathway.These results lay the foundation for elucidating the function of Cl SOD genes in stress tolerance and fruit development in watermelon.