Gregor Mendel, a friar by profession, cross-bred around 28,000 garden pea plants (Pisum sativum) and studied features such as shape and color of the pods and seeds to make discoveries about genetic inheritance. These experiments were performed 160 years ago, when he carefully studied seven traits in peas. Three of those traits included the shape and colour of their seeds and pods, and until now, scientists had no clue as to which genes were responsible for these traits. Now, Mendel’s breakthrough has a new chapter, ushering in a new era in genomic studies of these garden peas. What makes this new study all the more important is the potential of using garden peas as a source of plant-based protein.
Mendel famously cross-bred 28,000 garden pea plants, experimenting with seven traits in these plants. The experiment aimed to understand and identify how the traits were inherited by future generations of the pea plants. The concept of genes had not yet been discovered. However, Mendel predicted the presence of ‘factors’ which were inherited by the offspring, giving them their traits. Even today, scientists continue to study such Mendelian traits and have identified thousands of them in humans. However, many of these traits are not yet associated with a specific gene. Similarly, three of Mendel’s seven traits had no particular genetic recognition till now.
Noam Chayut, an applied crop geneticist at the John Innes Centre (JIC) in Norwich, UK, and a co-author of the current paper, states that he and the other team members decided that sequencing and computational tools had advanced sufficiently to tackle the final three genes. Using the JIC’s Germplasm Resource Unit alongside publicly available genomic data sets, the group collected and deep sequenced nearly 700 pea genomes. These genome sequences roughly had 155 million single-nucleotide polymorphisms (SNPs) — unit base-pair differences in the DNA sequences compared with the standard P. sativum genome.
The group identified the genes linked to the three remaining traits using selective breeding techniques and through genome-wide association studies. Notably, the researchers found that pea-pod colour is controlled by a gene that inhibits chlorophyll biosynthesis, leading to the formation of either green or yellow pods. They also noted the presence of two genes that may help control pod shape by inhibiting cell-wall thickening in the plant. The team also established that a deletion in the genetic code at a specific point in another gene can cause changes in the branching or clustering of flowers on the plants — a process called fasciation.
Apart from linking genes to the three remaining traits, the team conducted experiments on an additional 72 agriculturally important pea traits. Chayut notes that a substantial amount of information remains to be explored in the publicly available data. Pea protein is being viewed as an alternative source of protein, and researchers aim to examine the development of pea plants with higher protein content. Chayut is also interested in working with genes associated with pod size, seed protein content, and plant yield.
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