New strategies using autophagy modulators increase the efficiency of microspore embryogenesis

Among the challenges of current agriculture, it is the search for new varieties that are more resistant to pathogens, with greater productivity and better adaptability to climate change. In this sense, the plant nursery and seed companies use double-haploid plants (DHs) in their breeding programs; DH plants are obtained by microspore embryogenesis, which is the fastest way to achieve complete homozygosis in a single generation, reducing time and costs of the process. The process is induced in vitro by stress treatments that cause the haploid microspore to reprogram, acquire totipotency and produce embryos and plants H and DHs. However, its exploitation is limited in many crop and forest species due to its low or null efficiency, with the high rate of cell death being one of the main problems.

In a work published in the Journal of Experimental Botany by the group "Pollen biotechnology of crop plants" led by Dr. Pilar S. Testillano, belonging to the department of "Microbial and Plant Biotechnology" of the Centro de Investigaciones Biológicas, the activation of autophagy and proteases of the cathepsin family and its role in cell death during microspore embryogenesis of barley is demonstrated for the first time. Autophagy is a catabolic process by which the cell recycles cytoplasmic components, and has also been shown to play a role in the initiation and/or execution of cell death, although data on plants are very limited.
This study demonstrates that stress treatment that induces embryogenesis also causes in some cells a high production of reactive oxygen species (ROS), autophagy gene and protein induction (ATG5, ATG6, ATG8a), as well as an increase in autophagosomes and activity of several cathepsins, and their involvement in cell death. Additionally, it is determined that the use of autophagy modulators in the process allows reducing the level of cell death, increasing the efficiency of in vitro embryogenesis.

These findings open up a completely new intervention pathway with the potential to increase the in vitro production of embryos and double-haploid plants in crop species, especially those that are recalcitrant, with a very low response to the induction of in vitro embryogenesis, and their use for the search of new varieties.

Reference: Autophagy and cathepsins are activated and involved in cell death during stress-induced microspore embryogenesis in barley. Bárány I, Berenguer E, Solís MT, Pérez-Pérez Y, Santamaría ME, Crespo JL, Risueño MC, Díaz I, Testillano PS  [2018].  Journal of Experimental Botany, Published on line: January 4, 2018. DOI: 10.1093/jxb/erx455