Viroids: Circular RNAs Infectious Agents

Plants typically are resistant to non-specific pathogens thanks to the presence of a waxy cuticle covering the ______ cell layer

Fungi can penetrate directly into ______ cells or form hyphae over plant cells and between them

Bacterial and viral infections often require either damaged tissues, specialized structures (e.g., ______) for entering the cell

Plants rely on the innate immunity of each cell and systemic signals emanating from the sites of the infection and not on mobile defense cells and the somatic adaptive immune ______

Plants have so-called ______: outgrowths of the epidermis that prevent pathogen growth and penetration

Trichomes may contain ______ compounds or exert an inhibitory effect on the microbial hydrolytic enzymes involved in cell wall damage.

The cell wall consists of cellulose microfibrils and ______; it is reinforced with lignin and contains a significant amount of proteins that perform structural and enzymatic functions.

Antimicrobial plant compounds, which contain low-molecular-weight non-protein substances, are divided into two groups: phytoanticipins and ______.

Plants can also absorb and process exogenous hair- pin double-stranded RNAs (dsRNAs) to suppress the genes responsible for the life maintenance and viru- lence of viruses pathogenic to plants, fungi, and ______.

The number of R genes in the genome can amount to about 100, which is clearly not enough to recognize all possible ______.

Viruses infect all types of organisms, from plants and animals to bacteria and ______

Plant viruses mainly come in the form of single-stranded (ss) and double-stranded (ds) ______ viruses

The typical size of a plant virus is ______ nm

Viruses often express the proteins that ensure virion motility by modifying channels to facilitate the transmission of the infection to a ______ cell

In order to infect an entire plant, a virus must enter its ______ system

Fungi can penetrate directly into ______ cells or form hyphae over plant cells and between them

Bacterial and viral infections often require either damaged tissues, specialized structures (e.g., ______) for entering the cell

Plants have so-called ______: outgrowths of the epidermis that prevent pathogen growth and penetration

Plants rely on the innate immunity of each cell and systemic signals emanating from the sites of the infection and not on mobile defense cells and the somatic adaptive immune ______

Plants typically are resistant to non-specific pathogens thanks to the presence of a waxy cuticle covering the ______ cell layer

Fungi have a complex cell structure with a distinct nucleus and ______.

Fungi form a mycelium: a system of thin branching ______, which sometimes lacks intercellular septa and forms a syncytium.

Pathogenic fungi enter plants through damaged leaves and ______.

Biotrophs secrete effector molecules that suppress the plant’s ______.

Apressoria provide attachment of the fungus to the substrate, allowing the pathogen to penetrate the cell wall using a combination of mechanical force and enzymes that degrade the plant’s cell ______.

Viroids lack a protein envelope, instead they present covalently linked ssRNA molecules 200–500 nucleotides long, which is 50-80 times shorter than the viral genome. Viroids do not encode ______ and cannot replicate autonomously.

Viroids replicate via a ______ mechanism, with members of the families Pospiviroidae and Avsunviroidae replicating through an asymmetric and symmetric pathway, respectively.