Basifungin

Sphingolipids are essential in membrane trafficking and cellular homeostasis. Here, we show that sphingolipids containing very long-chain fatty acids (VLCFAs) promote homotypic vacuolar fusion in Saccharomyces cerevisiae. The elongase Elo3 adds the last two carbons to VLCFAs that are incorporated into sphingolipids. Cells lacking Elo3 have fragmented vacuoles, which is also seen when WT cells are treated with the sphingolipid synthesis inhibitor Aureobasidin-A. Isolated elo3Δ vacuoles show acidification defects and increased membrane fluidity, and this correlates with deficient fusion. Fusion arrest occurs at the tethering stage as elo3Δ vacuoles fail to cluster efficiently in vitro. Unlike HOPS and fusogenic lipids, GFP-Ypt7 does not enrich at elo3Δ vertex microdomains, a hallmark of vacuole docking prior to fusion. Pulldown assays using bacterially expressed GST-Ypt7 showed that HOPS from elo3Δ vacuole extracts failed to bind GST-Ypt7 while HOPS from WT extracts interacted strongly with GST-Ypt7. Treatment of WT vacuoles with the fluidizing anesthetic dibucaine recapitulates the elo3Δ phenotype and shows increased membrane fluidity, mislocalized GFP-Ypt7, inhibited fusion, and attenuated acidification. Together these data suggest that sphingolipids contribute to Rab-mediated tethering and docking required for vacuole fusion.

Faster vegetative growth and early maturity/harvest reduce plant life cycle time and are important agricultural traits facilitating early crop rotation. GA is a key hormone governing developmental transitions that determine growth speed in plants. An EAR‐motif repressor, SlERF36 that regulates various growth transitions, partly through regulation of the GA pathway and GA levels, was identified in tomato. Suppression of SlERF36 delayed germination, slowed down organ growth and delayed the onset of flowering time, fruit harvest and whole‐plant senescence by 10–15 days. Its over‐expression promoted faster growth by accelerating all these transitions besides increasing organ expansion and plant height substantially. The plant life cycle and fruit harvest were completed 20–30 days earlier than control without affecting yield, in glasshouse as well as net‐house conditions, across seasons and generations. These changes in life cycle were associated with reciprocal changes in expression of GA pathway genes and basal GA levels between suppression and over‐expression lines. SlERF36 interacted with the promoters of two GA2 oxidase genes, SlGA2ox3 and SlGA2ox4, and the DELLA gene, SlDELLA, reducing their transcription and causing a 3–5‐fold increase in basal GA3/GA4 levels. Its suppression increased SlGA2ox3/4 transcript levels and reduced GA3/GA4 levels by 30%–50%. SlERF36 is conserved across families making it an important candidate in agricultural and horticultural crops for manipulation of plant growth and developmental transitions to reduce life cycles for faster harvest.