miR168 influences phase transition, leaf epinasty, and fruit development via SlAGO1s in tomato

In Arabidopsis thaliana, Argonaute1 (AGO1) interacts with miR168 to modulate the small RNA regulatory pathway. However, the underlying mechanism of regulation and relationship between AGO1 and miR168 is poorly understood in the cash crop Solanum lycopersicum (tomato). We previously found that SlAGO1A and SlAGO1B were cleaved by miR168 in tomato. In this study, we show that SlAGO1A and SlAGO1B accumulate in miR168-sponge transgenic plants, and that expression of miR168-resistant SlAGO1A (4m-SlAGO1A) and SlAGO1B (4m-SlAGO1B) in tomato results in a series of defects affecting growth rate, floral timing, leaves, and fruit. Accumulation of miR156 was found when 4m-SlAGO1A was at an early developmental stage compared to the wild type and original SlAGO1A transgenic plants, and miR172 was highly expressed in adult 4m-SlAGO1A compared to the controls. In addition, the expression of multiple small RNAs was altered in 4m-SlAGO1A. Taken together, our data provide novel insights into the interaction between SlAGO1s and miR168 in determining growth rate, phase change, leaf epinasty, fruit initiation and expansion, and other developmental processes in tomato.

3-Chloro-5-trifluoromethylpyridine-2-carboxylic acid, a Metabolite of the Fungicide Fluopyram, Causes Growth Disorder in Vitis vinifera

The aim of this study was to investigate the effect of 3-chloro-5-trifluoromethylpyridine-2-carboxylic acid (PCA), a metabolite of the fungicide fluopyram, on grapevine. During spring and summer 2015, grapevine growth disorders were observed in several countries in Europe. An unprecedented herbicide-like damage was diagnosed on leaves and flowers, causing significant loss of harvest. This study proposes PCA as the causing agent of the observed growth disorders. PCA was shown to cause leaf epinasty, impaired berry development that leads to crop loss, and root growth anomalies in Vitis vinifera similar to auxin herbicides in a dose-dependent manner. Using both field trials and greenhouse experiments, the present study provides first evidence for a link between the application of fluopyram in vineyards 2014, the formation of PCA, and the emergence of growth anomalies in 2015. Our data could be useful to optimize dosage, application time point, and other conditions for an application of fluopyram without phytotoxic effects.