Table 1. Classification of plant RNase T2 proteins and proposed functions.

Class and Functions	Examples	References
Class I
Defense, antiviral	RNS1 (Arabidopsis), ZnRNase II (Zinnia elegans)	Kim et al., 2019; Trifonova et al., 2012
Defense, antimicrobial	RNase NE (Nicotiana tabacum)	Hugot et al., 2002
Defense, wounding	RNS1 (Arabidopsis), RNase LE (Solanum lycopersicum), OsRNS4 and OsRNS5 (O. sativa)	Hillwig et al., 2008; Gross et al., 2004; MacIntosh et al., 2010
Stress, drought/salinity	OsRNS4 (O. sativa), PvRNS3 (Phaseolus vulgaris)	Zheng et al., 2014; Diaz-Baena et al., 2020
Stress, P-starvation	RNS1 (Arabidopsis), EsRNS1 (Eutrema salsugineum), RNase LX and RNase LE (S. lycopersicum)	Bariola et al., 1999; Velasco et al., 2016; Köck et al., 1995
tsRNA synthesis	RNS1 and RNS3 (Arabidopsis)	Alves et al., 2017; Megel et al., 2019
Development/PCD	RNase LX (S. lycopersicum), ZRNase I (Z. elegans)	Lehmann et al., 2001; Lers et al., 2006; Fukuda 2000
Class II
RNA/nucleotide salvage	RNS2 (Arabidopsis)	Hillwig et al., 2011a
Stress, P-starvation	RNS2 (Arabidopsis)	Bariola et al., 1999
Class III
Self-incompatibility	S-RNases (Solanaceae, Plantaginaceae, Rubiaceae, Rosaceae)	Ramanauskas and Igić, 2017
Defense, antimicrobial	S1-RNase and SX-RNase (Petunia hybrida), SA2-RNase (Nicotiana alata)	Hillwig et al., 2011b; Silva et al., 2020
Stress, P-starvation	NnSR1 and SX-RNase (N. alata)	Rojas et al., 2015; Rojas et al., 2018