Genome-wide Characterization, Expression Patterns And Functional Analysis Of The IMPα/β And LYK Gene Families In Tomato

Nucleocytoplasmic transport receptors regulate various cellular activities by selective bidirectional transport of macromolecules across the nuclear envelope, such as signal perception/transduction, protein interaction and gene expression. The important significance of nucleocytoplasmic transport via importina and importinβ (IMPα/β) has been exhibited in a wide spectrum of biological processes. Receptor-like protein kinases containing LysM motif (LYKs) participate in the establishment of symbiotic relationship between host plants and their specific microorganisms mainly by identifying signaling molecules containing N-acetyl glucosamine base, and play an important role in plant growth and disease resistance response. This study aimed to identify the IMPα/β and LYK families in tomato and to characterize their possible inovolvement in disease resistance using virus-induced gene silencing (VIGS) approach.We isolated and identified six genes encoding for SlIMPa proteins, which mainly consist of IBB domain and 8-10 ARM tandem repeats, and fifteen genes encoding for IMPβ proteins, which are composed of 19-20 similar HEAT repeats. The analysis of expression patterns indicate that these SlIMPα/β genes expressed differently after treatment with Botrytis cinerea, Pseudomoas syringae pv. tomato (Pst) DC3000 or hormone signaling molecules including salicylic acid (SA), jasmonic acid (JA) or 1-aminocyclopropane-1-carboxylic acid (ACC). SlIMPα1 and SlIMPα6 were induced by SA, JA and ACC, whereas SlIMPα1、SlIMPα2、SlIMPα3、 SlIMPα6 were induced by B.cinerea and Pst DC3000. However, the expression patterns of SlIMPβs were complicated. Using VIGS approach, we silenced individual SlIMPα/β gene to knockdown the transcript levels and analyzed the disease phenotypes. The results indicated that silencing of SlIMPα1 in tomato plants result in spontaneous induction of reactive oxygen species (ROS). The expression levels of SlRbohI and SlCAT1 were extremely significant increased as compared with those in control plants, but the expression levels of SISOD was extremely significant decreased.SlIMPα6-silenced plants reduced the resistance to B. cinerea. SlIMPβ3-, SlIMPβ6- and SlIMPβ9 -silenced plants displayed changed morphological phenotype. SlIMPβ13-silenced plants reduced the resistance to B. cinerea. These results indicate that the tomato SlIMPαs/βs play important roles in plant normal growth and development and resistance against B. cinerea.We isolated and identified 14 SILYK genes in tomato. After treatment with B. cinerea, Pst DC3000 or hormone signaling molecules including SA, JA or ACC, these SILYK genes exhibited different expression patterns. Compared with the control, only SILYK7 transcriptional expression level had no obvious difference when treatment with SA, the same as SILYK5 and SILYK11 transcriptional expression level when treatment with JA. Additionly, the other genes were significantly induced by SA or JA. Under the ACC treatment, transcriptional levels of the most genes-showed no obvious change. Using VIGS approach, we silenced individual SILYK gene. The results indicate that the SILYK1-silenced plants showed enhanced resistance to B. cinerea, while the SILYK11- and SlLYK13-silenced plants showed increased susceptibilities to B. cinerea. Taken together, our results demonstrate that the tomato SILYKs also play different roles in resistance against B. cinerea.