Comparative de novo transcriptome profiles in Asparagus officinalis and A. kiusianus during the early stage of Phomopsis asparagi infection

Asparagus kiusianus , an important wild relative of cultivated asparagus ( A . officinalis ), exhibits resistance to stem blight disease caused by Phomopsis asparagi . However, the mechanisms underlying this resistance are not understood and no transcriptomic or genetic resources are available for this species. De novo transcriptome sequencing of A . officinalis and A . kiusianus stems was performed 24 h after inoculation with P . asparagi . In total, 35,259 and 36,321 transcripts were annotated in A . officinalis and A . kiusianus , respectively. 1,027 up-regulated and 752 down-regulated transcripts were differentially expressed in the two Asparagus species. RNA sequencing data were validated using quantitative real-time reverse transcription PCR. Several defense-related genes including peroxidase 4 , cationic peroxidase SPC4 - like , pathogenesis - related protein - 1 - like , and jasmonic acid biosynthesis and signaling-related genes including phospholipase D alpha 1 , 12 - oxophytodienoate reductase and jasmonate - induced protein 23 KD were up-regulated in A . kiusianus relative to A . officinalis . In addition, infected A . kiusianuns exhibited a substantial increase in jasmonic acid and methyl jasmonate relative to A . officinalis . Peroxidase activity was significantly elevated in infected A . kiusianus compared with infected A . officinalis . Our transcriptomic database provides a resource for identifying novel genes and molecular markers-associated with Phomopsis disease resistance and will facilitate breeding and improvement of cultivated asparagus varieties.