Table 1.
Abilities of Soybean mosaic virus (SMV) strains N, G7 and G7d, as well as their derivative PIPO, P3 and PIPO+P3 mutants ,to infect systemically rsv1‐ and Rsv1‐genotype soybeans following biolistic or mechanical inoculations.*
| Viruses/mutants | Substitutions† | rsv1 | Rsv1 | |||
|---|---|---|---|---|---|---|
| Nucleotide | P3 (aa) | PIPO (aa) | Lee68 | Williams82 | L800 | |
| SMV‐N | (3/3)‡ 3/3§ | (4/4) 4/4 | (0/10) 0/4 | |||
| SMV‐G7 | (3/3) 9/9 | (3/3) 3/3 | (3/3) 4/4 | |||
| SMV‐G7d | ND¶ 6/6 | (3/3) 6/6 | (3/3) 4/4 | |||
| SMV‐NC30Y | G2970A | A947T** | C30Y | ND 5/5 | (3/4) 5/5 | (2/3) 6/6 |
| SMV‐NC30R | T2969C | NA †† | C30R | (0/2) ND | (2a ‡‡/6) ND | (0/7) 0/3 |
| SMV‐NE35K | G2984A | NA | E35K | (2/2) 3/3 | (6/6) 4/4 | (1a/5) 1a/10 |
| SMV‐NK65Q | A3074C | NA | K65Q | (3/3) 3/3 | (4/4) 2a/2 | (0/4) 0/4 |
| SMV‐NE35K+K65Q | G2984A+A3074C | NA | E35K | (3/3) 6/6 | (4/4) 3/3 | (0/4) 1a/10 |
| K65Q | ||||||
| SMV‐NE35R | G2984A+A2985G | K952E | E35R | ND 3/3 | (6/6) 3a/3 | (0/4) 0/6 |
| SMV‐NE35G | A2985G | K952E | E35G | ND 7/7 | (4/4) 7/7 | (0/3) 1a/7 |
| SMV‐NK816E+E35K | A2577G+G2984A | K816E | E35K | ND 3/3 | (4/4) 4/4 | (3/4a) 6/6 |
| SMV‐G7Y30C | A2973G | T948A | Y30C | ND 3/3 | (3/3) 4a/4 | (0/4) 1a/12 |
| SMV‐G7Y30H | T2972C | NA | Y30H | (1/3) 5/5 | (5/6) 4/5 | (2a/7) 6/6 |
| SMV‐G7K35E | A2987G | NA | K35E | (3/3) 3/3 | (4/4) 3/3 | (4a/4) 7/8 |
| SMV‐G7Q65K | C3077A | NA | Q65K | (3/3) 3/3 | (3/3) 3/3 | (4a/4) 6/8 |
| SMV‐G7K35R | A2988G | K953E | K35R | ND 3/3 | (4/4) 3/3 | (3/4) 5/5 |
| SMV‐G7K35E+Q65K | A2987G+C3077A | NA | K35E | (3/3) 6/6 | (4/4) 3/3 | (4a/4) 9/9 |
| Q65K | ||||||
| SMV‐G7dY30C | A2973G | T948A | Y30C | ND 4/5 | (6/6) 2a/4 | (0/4) 1a/4 |
| SMV‐G7dR35E | A2987G+G2988A | E953K | R35E | ND 5/5 | (6/6) 3a/4 | (3/4) 5/5 |
| SMV‐G7dR35K | G2988A | E953K | R35K | ND 5/5 | (7/7) 2a/2 | (3/4) 4/4 |
| SMV‐G7dR35G | A2987G | NA | R35G | ND 6/6 | (3/3) 7a/7 | (4/4) 4/4 |
| SMV‐G7dQ65K | C3077A | NA | Q65K | ND 3/3 | (4/4) 3/3 | (4/4a) 4/4 |
| SMV‐NK816E | A2577G | K816E | NA | ND 3/3 | (4/4) 4/4 | (2a/4) 6/6 |
| SMV‐NV822M | G2595A | V822M | NA | ND 5/5 | (3/3) 4/4 | (2/3) 4a/4 |
| SMV‐NR945G ** | A2964G | R945G | K28R | ND 5/5 | (3/3) 2/3 | (2/3) 4/5 |
| SMV‐NA947V ** | C2971T | A947V | NA | ND 6/6 | (3/3) 7/7 | (3/3) 8/9 |
| SMV‐NP948L ** | C2974T | P948L | NA | ND 7/7 | (3/3) 7/7 | (1/4) 4/5 |
| SMV‐NV1045A ** | T3265C | V1045A | NA | ND 6/6 | (3/3) 3/3 | (1/3) 4/5 |
For biolistic inoculation, plasmid containing full‐length infectious cDNA clones was delivered into fully expanded primary leaves of 2‐week‐old soybean seedlings. For mechanical inoculation, infectious sap from biolistically inoculated Williams82 (rsv1) was used as inoculum and rub‐inoculated onto fully expanded primary leaves of 2‐week‐old soybean seedlings. The inoculated plants were maintained in a growth chamber (22 °C) until evaluation for infection based on symptom expression. Absence of virus in asymptomatic plants was confirmed by antigen‐coated indirect enzyme‐linked immunosorbent assay (ELISA).
The positions of nucleotides or amino acid (aa) substitutions are based on genomic sequences of SMV strains N, G7 and G7d (GenBank accession nos. D00507, AY216010 and AY216987, respectively). For the position of PIPO amino acids, see 1, 3.
Number of plants systemically infected/number of plants inoculated biolistically.
Number of plants systemically infected/number of plants sap inoculated mechanically.
Not done.
Published data (Hajimorad et al., 2011).
Not affected (substitution is either synonymous or located outside pipo).
The superscript letter ‘a’ indicates that, for each mutant, total RNA was extracted from one infected plant of the indicated genotype and subjected to reverse transcriptase‐polymerase chain reaction (RT‐PCR). The stability of the introduced mutation(s) and the lack of any newly emerged mutations in progeny viruses were confirmed by sequencing the entire P3 cistron of progeny viruses. Infection of one Williams82 (Rsv1) with SMV‐NC30R was associated with an additional mutation in P3 at position C2970T, which resulted in A947S and C30L substitutions in P3 and PIPO, respectively. Progeny viruses from the second infected Williams82 with SMV‐NC30R lacked the introduced mutation and the mutation had reverted to the wild‐type. No mutation in P3 of the progenies derived from the single infected L800 (Rsv1) inoculated biolistically with SMV‐NE35K was detected; however, these progenies failed to infect additional L800 (Rsv1) when inoculated mechanically. Progeny from L800 (Rsv1) mechanically inoculated with sap derived from biolistically inoculated Williams82 (rsv1) with SMV‐NE35K contained a sequence polymorphism at position 2577. Thus, both codons AAG and GAG encoding lysine (Lys) and glutamic acid (Glu), respectively, were present at codon position 816 located in P3 (Fig. S1). Infection of L800 (Rsv1) with SMV‐NE35K+K65Q was associated with C2671T substitution, which resulted in A847V mutation in P3. Infection of a single mechanically inoculated L800 (Rsv1) with SMV‐G7Y30C was associated with only limited vein necrosis on the third trifoliate leaf at 21 days post‐inoculation without any sign of necrosis on the leaf blade or any other visible symptoms; however, no additional mutation in P3 was detected. Infection of L800 (Rsv1) by SMV‐NE35G was associated with a sequence polymorphism in P3 at position 2709, where both TCA and ACA codons encoding serine (Ser) and threonine (Thr), respectively, were present at polyprotein position 860. No newly emerged mutations in P3 cistrons of other progenies derived from any of the other molecularly cloned mutant viruses were detected.