Page 6 - Plant Gene and Trait

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Expression of two SAT isoforms namely LcSAT1 and
LcSAT2 was also detected (Figure 1). mRNA trans-
cripts of both isoforms changed non-significantly
(P >0.05) between the mutant lines and control variety.
Figure 1 mRNA gene expression of OAS-TL1, OAS-TL2,
SAT1 and SAT2 isoforms of variety L 414, lentil mutants and
their segregating progenies
Note: Lentil EF1- α was used as housekeeping gene. Lane
1-control variety L 414, lane 2-cysLc1 mutant, lane 3-cysLc2
mutant, lane 4-F1 plant of control×cysLc1 mutant, lane 5-F1
plant of control×cysLc2 mutant, lane 6, 7-F2-recessive
homogygous plant (cysLc1 cysLc1) recovered from control×
cysLc1 mutant (OAS-TL 1 transcripts not detected), lane 8 and
9- F2-recessive homogygous (cysLc2 cysLc2) plant recovered
from control×cysLc2 mutant (OAS-TL2 transcripts absent),
lane 10- F1 plant (normal) of cysLc1×cysLc2 mutant, lane 11,
12-F2 plant with normal OAS-TL expressions, lane 13-F2
progeny plant with mutant phenotype (cysLc1, no OAS-TL 1
transcript), 14- F2 plant with mutant phenotype (cysLc2,
OAS-TL2 transcript absent), M- 100bp DNA marker (→200bp)
1.4 GSH, GSSG and GSH-redox state
Compared to control, GSH content was reduced by
4.4-fold in cysLc1 and by 2.8-fold in cysLc2 but
GSSG level was enhanced by nearly 2-fold in both
cases (Table 1). Low GSH level but increasing GSSG
content led to decline in GSH-redox state in roots of
both the mutants (Table 1).
1.5 Genetic basis of cysteine-deficient mutants
All F1 progeny plants (190) obtained from
control×mutants exhibited normal (control like)
growth accompanied by usual seed cysteine level
(mean 19.3±1.9 nmol/g fresh weight). The trait was
segregated in F2 and corresponding test crosses
(F1×mutant). The segregating traits exhibited good fit
to 3 (151 plants, normal growth and cysteine level
mean 20.8±1.9 nmol/g fresh weight): 1 (52 plants,
poor growth, deficient seed cysteine 5.8±1.0 nmol/g
fresh weight) ratio in F2 (χ2 = 0.04, 1 df, P<0.05) and
1:1 (41 normal: 37 mutant, χ2=0.20, 1 df, P <0.05) in
back crosses. However, all F1s (178 plants) derived
from cysLc1×cysLc2 exhibited normal growth and
usual level of seed cysteine (mean 22.3±1.2 nmol/g
fresh weight) but segregated into normal (69 plants,
cysteine level mean 21.6±2.1 nmol/g fresh weight) and
mutant phenotype (43 plants, cysteine level mean
6.1±1.1 nmol/g fresh weight), exhibiting good fit
(χ2=1.31, P<0.05) to 9 (normal phenotype):7 (mutant
phenotype) ratio in F2. Gene expression analysis
confirmed down-regulation of either OAS-TL1 or
OAS-TL2 isoform transcripts in plants showing
mutant phenotype but normal expressions of both
isoforms in plants exhibiting control like phenotype in
segregating F2 progeny (Figure 1).
2 Discussion
2.1 cysLc1 and cysLc2: two unique biochemical
mutants isolated in lentil
Induced mutagenic techniques have earlier been
successfully used to isolate novel biochemical mutants
exhibiting modulations in antioxidant defense
components in edible legumes such as lentil, common
beans, and grass pea (Talukdar, 2012a; 2012b;
Talukdar and Talukdar, 2013a; 2013b). In present case,
both the mutants are unique in legumes, containing
very low seed cysteine level and deficiency in a major
cysteine-synthesizing enzyme in photosynthetic organ.
Biochemical mutants with altered carbohydrate and
reducing sugar content, protein and amino acid
methionine content, amylase inhibitor deficient and
anti-nutritional contents like phytic acid have been
reported in pea, black gram, pigeon pea, winged bean
and soybean (Chougule et al., 2004; Gandhi et al.,
2012; Bhalerao and Kothekar, 2013; Kumari et al.,
2014), but none of the mutants were studied in respect
of sulphur metabolisms. A sulphur deficiency-induced
gene, sdi1 has been characterized in wheat (Howarth
et al., 2009), but this type of work has not been carried
out in grain legumes. Along with severe deficiency in
seed cysteine content, both the present mutants
exhibited significant retardation in growth habits,
PLANT GENE AND TRAIT