*Article Agrobacterium***-Mediated Gene Transient Overexpression and** *Tobacco Rattle Virus* **(TRV)-Based Gene Silencing in Cassava**

#### **Hongqiu Zeng <sup>1</sup> , Yanwei Xie <sup>1</sup> , Guoyin Liu <sup>1</sup> , Yunxie Wei <sup>1</sup> , Wei Hu 2,\* and Haitao Shi 1,\***


Received: 17 July 2019; Accepted: 13 August 2019; Published: 15 August 2019

**Abstract:** *Agrobacterium*-mediated transient expression and virus-induced gene silencing (VIGS) are very useful in functional genomics in plants. However, whether these methods are effective in cassava (*Manihot esculenta*), one of the most important tropical crops, remains elusive. In this study, we used *green fluorescent protein* (*GFP*) and β*-glucuronidase* (*GUS*) as reporter genes in a transient expression assay. *GFP* or *GUS* could be detected in the infiltrated leaves at 2 days postinfiltration (dpi) and were evidenced by visual *GFP* and *GUS* assays, reverse-transcription PCR, and Western blot. In addition, *phytoene desaturase* (*PDS*) was used to show the silencing effect in a VIGS system. Both *Agrobacterium* GV3101 and AGL-1 with *tobacco rattle virus* (TRV)-*MePDS*-infiltrated distal leaves showed an albino phenotype at 20 dpi; in particular, the AGL-1-infiltrated plants showed an obvious albino area in the most distal leaves. Moreover, the silencing effect was validated by molecular identification. Notably, compared with the obvious cassava mosaic disease symptom infiltrated by *African*-*cassava*-*mosaic*-*virus*-based VIGS systems in previous studies, TRV-based VIGS-system-infiltrated cassava plants did not show obvious virus-induced disease symptoms, suggesting a significant advantage. Taken together, these methods could promote functional genomics in cassava.

**Keywords:** *agrobacterium*; transient expression; virus-induced gene silencing (VIGS); *tobacco rattle virus* (TRV); cassava (*Manihot esculenta*)
