Behzad Ahmadi

Isolated Microspore Culture and Its Applications in Plant Breeding and Genetics

Isolated microspore culture (IMC) represents a unique system of single cell reprogramming in plants wherein a haploid male gametophyte, the microspore, switches its default gametophytic developmental pathway toward embryogenesis by specific stress treatment. The application of a stress treatment(s) is necessary for efficient embryogenesis induction. Depending on species, microspores are often induced by cold and heat shock, osmotic stress, starvation, anti-microtubular agents, stress hormones, antibiotics, or polyamines. This technique (IMC) is likely to remain as a well-known method in plant breeding since it allows for the rapid production of completely homozygous lines while, in the context of developmental biology, it allows for in vitro embryogenesis to be explored in greater detail. Isolated microspores also represent ideal recipients for several gene transfer techniques including electroporation, microprojectile bombardment, and Agrobacterium-mediated transformation. IMC is also extensively used for genetic studies, i.e., studying inheritance of quantitative traits, quantitative trait loci (QTL) mapping, and genomics and gene identification, for mutation and selection and also used for producing reversible male-sterile lines. Male sterility avoids the labor costs of manual emasculation and serves as a molecular strategy for transgene containment by preventing pollen release to the environment. Combination of this technique with doubled haploid (DH) production leads to an innovative environmentally friendly breeding technology. In addition, the usefulness of DHs for reverse breeding program, an applied plant breeding technique introduced to directly produce parental lines for any hybrid plant, is also generally discussed.

Microspore embryogenesis in Brassica: calcium signaling, epigenetic modification, and programmed cell death

Main conclusionStress induction followed by excessive calcium influx causes multiple changes in microspores resulting in chromatin remodeling, epigenetic modifications, and removal of unwanted gametophytic components via autophagy, switching microspores towards ME.In Brassica, isolated microspores that are placed under specific external stresses can switch their default developmental pathway towards an embryogenic state. Microspore embryogenesis is a unique system that speeds up breeding programs and, in the context of developmental biology, provides an excellent tool for embryogenesis to be investigated in greater detail. The last few years have provided ample evidence that has allowed Brassica researchers to markedly increase their understanding of the molecular and sub-cellular changes underlying this process. We review recent advances in this field, focusing mainly on the perception to inductive stresses, signal transduction, molecular and structural alterations, and the involvement of programmed cell death at the onset of embryogenic induction.