Expression profile of protein fractions in the developing kernel of normal, Opaque-2 and quality protein maize

Abstract

Maize protein quality is determined by the composition of its endosperm proteins, which are classified as nutritionally poor zeins (prolamin and prolamin-like) and nutritionally rich non-zeins (albumin, globulin, glutelin-like, and glutelin). Protein quality is considerably higher in opaque-2 mutants due to increased content of non-zeins over zeins. However, the opaque-2 endosperm is soft, which leads to poor agronomic performance and post-harvest infestation. Endosperm modification of opaque-2 had led to the development of Quality Protein Maize (QPM), which has higher protein quality along with hard kernel endosperm. The present study was planned to analyze the expression dynamics of different protein fractions in the endospem of developing maize kernel in normal, opaque-2 and QPM in response to the introgression of endosperm modifiers. Results revealed that albumin and globulin content decreases, whereas, prolamin, prolamin-like, glutelin-like, and glutelin content increases with kernel maturity. It has been observed that opaque-2 mutation affects protein expression at initial stages, whereas, the effect of endosperm modifiers was observed at the intermediate and later stages of kernel development. It has also been noted that prolamin, glutelin, and glutelin-like fractions can be used as quick markers for quality assessment for differentiating QPM varieties, even at the immature stage of kernel development. Overall, the present study implicates the role of different protein fractions in developing and utilizing nutritionally improved maize varieties.

Elucidation of zein isoforms associated with high protein quality traits for targeted improvement in maize‐based nutrition

“…Zein content was the highest in normal lines (51.31%), intermediate in QPM (28.08%), and the lowest in opaque-2 (19.5%), whereas nonzein content was the highest in opaque-2 (75.73%), intermediate in QPM (70.35%), and the lowest in normal lines (45.11%). As reported earlier, prolaminlike content is known to contribute to endosperm modification in QPM as the maximum prolamin-like content was accumulated in QPM (18.04%), intermediate in normal (11.14%), and the least in opaque-2 (10.85%) (Sethi et al, 2021). On the basis of the biochemical and physiological parameters, the three lines under consideration show variability in terms of texture, zein content, and nonzein content, which was further examined by SDS-PAGE and 2D-PAGE.…”

“…Therefore, pellagra is caused by maize consumption due to the high amount of zein, especially 19, 22 kDa zeins, which have lower amounts of Trp and high amounts of Leu and Ile (Badawy et al, 2014). Therefore, the overall nutritional quality of opaque-2 and QPM lines is contributed by both higher expressions of nonzeins (Sethi et al, 2021) and higher accumulation of low-molecular-weight zeins in comparison to normal maize.…”

“…Retention of less moisture content by QPM lines will lead to tolerance to stored grain insect pests. Also, three lines, including normal (HKI‐1105N), opaque‐2 (DQI‐1001), and QPM (HKI‐1105) showing maximum variability for protein quality were selected for 2D‐PAGE analysis (Sethi et al, 2020, 2021). Before 2D‐PAGE analysis, the total zeins isolated were separated by SDS‐PAGE.…”

Unraveling the role of δ‐zeins in methionine bio‐fortification of maize

“…The intensity of the bands was increased with kernel maturity in both the high and low-methionine lines, indicating their increased accumulation with grain maturity. The synthesis of zein proteins starts from 10 DAP during kernel development and increases toward maturity and the zein proteins are the major seed storage protein in maize kernel (Sethi et al, 2021). Zein proteins play an important role in protein body (PB) formation.…”

Genetic and molecular understanding for the development of methionine-rich maize: a holistic approach

“…Three cycles of screening and recurrent selection of maize lines can be used to sort the germplasm into different groups based on desired traits. As described in the previous study ( Sethi et al., 2021 ), the temporal expression of δ-zein after pollination can be evaluated to determine the differential pattern of protein accumulation during seed development. It indicates the developmental stage at which maize seeds have maximum Met content that can be used as selection criteria for screening of Met-rich lines.…”