GSE98055
Differential small RNA expression upon induction and establishment of Tuxpeño maize embryogenic callus cultures
Purpose: Maize somatic embryogenesis is usually required to achieve genetic transformation and represents an important alternative in plant development. Although many embryogenesis-related genes have been studied in this model, the molecular mechanisms underlying cell dedifferentiation and further plant regeneration are not completely understood. Methods: Immature embryos smRNA profiles of 15-day-after-pollination (IE) and Embryogenic Callus from one (C1), four (C4), and ten months (C10) were generated by deep sequencing, using Illumina GAIIx. The sequence reads that passed quality filters were analyzed with two methods: Bowtie 1.1.2 and ShortStack 3.4. qRT–PCR validation for selected miRNAs was performed using SYBR Green assays. Results: We used high throughput sequencing to explore the sRNA populations during maize embryogenic callus induction and established subcultures from the Mexican cultivar VS-535, Tuxpeño landrace. We detected readjustments in 24 nt and 21-22 nt sRNA populations during the embryogenic callus establishment and maintenance. miRNAs related to stress response substantially increased upon callus proliferation establishment, correlating with a reduction in some of their target levels. On the other hand, while 24 nt-long hc-siRNAs derived from transposable retroelements transiently decreased in abundance during the embryogenic callus establishment, a population of 22 nt- hc-siRNAs increased. This was accompanied by reduction in transposon expression in the established callus subcultures. Conclusions: Stress- and development-related miRNAs are highly expressed upon maize EC callus induction and during maintenance subcultures, while miRNAs involved in hormone response only transiently increase during induction. The establishment of proliferative maize embryogenic callus is accompanied by important readjustments in the length of hc-siRNAs mapping to LTR retrotransposons, and their expression regulation. Overall design: Immature embryos smRNA profiles of 15-day-after-pollination (IE) and Embryogenic Callus from one (C1), four (C4), and ten months (C10) were generated by deep sequencing, using Illumina GAIIx.