Figure 2.

Regulation of callose deposition at plasmodesmata in susceptible (60444) and resistant (KBH 2006/18) cassava varieties after Cassava brown streak virus (CBSV) infection. (a) Schematic depiction of a plasmodesmata used by viruses for intercellular movement. Also shown are genes encoding key enzymes significantly regulated after infection (BG3, GLUCANASE, encoding a callose‐degrading β‐1,3‐glucanase; GSL4, GLUCAN SYNTHASE‐LIKE 4, encoding a callose synthesis enzyme; PDLP1, PLASMODESMATA LOCATED PROTEIN 1, encoding a protein involved in virus movement across the plasmodesmata and in callose synthesis; ANKs, ANKYRIN REPEAT FAMILY PROTEINS, encoding proteins that are negative regulators of callose deposition) with their fold changes based on RNA‐sequencing (RNA‐seq) analysis at 28 days after grafting (dag). (b) Top: reverse transcription‐quantitative polymerase chain reaction (RT‐qPCR) analysis of BG3 mRNA at 60 dag. 60444 leaves were symptomatic for virus infection at this time point. Bottom: BG3 enzymatic activity also increases significantly after infection in 60444 and is unchanged in KBH 2006/18 at 60 dag. (c) Aniline blue staining for detection of callose deposits. Leaf samples from 60444 and KBH 2006/18 were stained and visualized using a confocal laser scanning microscope at 400× magnification. Callose deposits are visible as small bright dots along the cell walls (white arrowheads). (d) Top: quantification of callose deposits at plasmodesmata (Pd) in 60444 and KBH 2006/18 at 60 dag, observed after aniline blue staining and microscopy. Bottom: number of callose deposits found in microscopic images. Infection decreases the number of callose deposits in 60444. P values indicate statistical significance: * P < 0.05; **P < 0.01, unpaired t‐test.