The unusual cabbage mutation that could boost crop yield

Subject: Science and tech

Section: Biotech

Context:

The males of plants as diverse as cabbage, cauliflower, broccoli, tomato, and rice can be made sterile by deleting a very small part of their genome’s DNA.
This deletion holds the promise of significantly boosting crop yields through a phenomenon known as heterosis.

Understanding Genetics

The cabbage plant (Brassica oleracea) genome contains approximately 1.06 billion base pairs distributed across 18 chromosomes.Each chromosome pair, derived from pollen and egg, shares a mostly identical sequence.

Role of Genes:

Genes are well-defined DNA sequences, typically spanning a few thousand base pairs.When expressed, a gene’s segment is transcribed into RNA, which serves as the blueprint for protein synthesis.
Protein Production: RNA is processed by cellular machinery called ribosomes, directing the assembly of amino acids into proteins.

Role of Sterility in Hybrid Vigor

Finding of Ms-cd1: Around 44 years ago, a cabbage plant with a natural mutation known as Ms-cd1 was identified.This mutation rendered the plant male-sterile, with a crucial twist: the eggs of the mutant plant could still be fertilized by pollen from normal plants, yielding normal seeds.
Hybrid Seeds: All seeds from mutant plants resulted from out-crossing, where eggs were fertilized by pollen from different strains.Such hybrid seeds, also called out-cross seeds, give rise to more robust plants with enhanced vigor, known as heterosis.
Dominant Mutation: The Ms-cd1 mutation was found to be dominant, meaning its presence in just one chromosome of the pair caused male sterility, regardless of the other chromosome’s status.
Recessive Mutations: The researchers demonstrated that mutations in both copies of the Ms-cd1 gene were necessary for male fertility.In such cases, the mutations became recessive.

Crucial Missing Base-Pair

Genetic Mapping: Through genetic mapping, researchers identified a crucial distinction between the mutated and non-mutated Ms-cd1 genes. The mutated gene lacked a single DNA base pair in its promoter region.
Promoter’s Role: The promoter sequence binds to regulatory proteins that control when and in which cells a gene is transcribed into RNA.
ERF Binding: In the mutated gene, this missing base-pair disrupted its binding to the regulatory protein ERF, allowing the Ms-cd1 gene to remain expressed, leading to male sterility.
Fine-Tuning of Protein Levels: Proper pollen development depends on a precise balance of Ms-cd1 protein levels, with ERF binding regulating its expression at different stages of development.