Watson, J. M. | bioRxiv Science

bioRxiv2019

Viola unica (Violaceae L.), a very rare, high elevation, single site new species endemic to the northern semi-desert Altiplano of Chile

While examining the Viola collection at the herbarium (SGO) of the Museo Nacional de Historia Natural (MNHN), Santiago, we encountered a folder with a single unidentified specimen consisting of a solitary rosette. It had been found in northern Chile near the border with Bolivia, where considerable mining activity takes place. The plant appeared to differ from all others related to it as known to ourselves, and on investigation it did indeed prove to be undescribed. It is presented herein, together with a detailed analysis and preliminary partial revision of related taxa, including a key.

plant biology↗

bioRxiv2019

A hypomorphic allele of telomerase reverse transcriptase uncovers the minimal functional length of telomeres in Arabidopsis.

Despite the essential requirement of telomeric DNA for genome stability, the length of telomere tracts between species differs by up to four orders of magnitude, raising the question of the minimal length of telomeric DNA necessary for proper function. Here we address this question using a hypomorphic allele of the telomerase catalytic subunit, TERT. We show that although this construct partially restored telomerase activity to a tert mutant, telomeres continued to shorten over several generations, ultimately stabilizing at a bimodal size distribution. Telomeres on two chromosome arms were maintained at a length of 1kb, while the remaining telomeres were maintained at 400 bp. The longest telomeres identified in this background were also significantly longer in wild type populations, suggesting cis-acting elements on these arms either promote telomerase processivity or recruitment. Genetically disrupting telomerase processivity in this background resulted in immediate lethality. Thus, telomeres of 400 bp are both necessary and sufficient for Arabidopsis viability. As this length is the estimated minimal length for t-loop formation, our data suggest that telomeres long enough to form a t-loop constitute the minimal functional length.

genetics↗