Screening for Plant Regulators Modulating the Early Disease-State Transition of Cassava Brown Streak Disease (CBSD) Using Dynamic Network Biomarker (DNB)

The sustainability of cassava production is one of the important missions for global food and
energy security, especially in Africa and Asia. Cassava brown streak disease (CBSD), caused by the
cassava brown streak virus (CBSV), is one of the major factors contributing to significant yield losses up
to 70%. Early screening for CBSD detection is an effective strategy to reduce viral spreading and
minimize economic losses. Despite several genes associated to CBSV infection were revealed by
conventional transcriptome analysis, these differentially expressed genes (DEGs) were often proposed
from plants with mild or severe symptoms, leading to the early response genes remaining unidentified.
Here, we utilized a Dynamic Network Biomarker (DNB) approach to identify regulators or DNB genes
that serve as an early molecular signal of normal-to-disease transition using time series transcriptome
datasets of susceptible cassava cultivar under control and CBSV infection condition. The result revealed
that 24 DNB genes influenced the normal-to-disease transition at 24 hours after viral infection, before
the onset of the CBSD symptoms. The DNB genes mainly consisted of enzymatic genes and
transcriptional factors (TFs) participating in various biological processes, such as isoprenoid
biosynthetic, photosynthesis, responding to superoxide radicals, and nucleotide biosynthesis.
Interestingly, the 3 DNB genes, aminodeoxychorismate lyase (ADC lyase), dUTP-Pyrophosphatase-
Like1 (dUTPase), and Hydroxymethylglutaryl-Coa Synthase (HMGS), were hypothesized to be an early
defense response for a competition of nucleotide usage between cassava and CBSV which subsequently
causes the CBSD. This study provides the potential regulators as early warning signals of CBSV
infection in cassava.