The circadian clock protein Frequency (FRQ) feedback-regulates its own expression by inhibiting its transcriptional activator, White Collar Complex (WCC). We present evidence that FRQ regulates the bulk of WCC through modulation of its phosphorylation status rather than via direct complex formation. In the absence of FRQ, WCC is hypophosphorylated and transcriptionally active, while WCC is hyperphosphorylated and transcriptionally inactive when FRQ is expressed. The phosphorylation status of WCC changes rhythmically over a circadian cycle. Dephosphorylation and activation of WCC depend on protein phosphatase 2A (PP2A), and WCC is a substrate of PP2A in vitro. Hypophosphorylated WCC binds to the clock box of the frq promoter even in the presence of FRQ, while binding of hyperphosphorylated WCC is compromised even when FRQ is depleted. We propose that negative feedback in the circadian clock of Neurospora is mediated by FRQ, which rhythmically promotes phosphorylation of WCC, functionally equivalent to a cyclin recruiting cyclin-dependent kinase to its targets.

Grapevine leafroll disease (GLD) is one of the most important grapevine viral diseases affecting grapevines worldwide. The impact on vine health, crop yield, and quality is difficult to assess due to a high number of variables, but significant economic losses are consistently reported over the lifespan of a vineyard if intervention strategies are not implemented. Several viruses from the family Closteroviridae are associated with GLD. However, Grapevine leafroll-associated virus 3 (GLRaV-3), the type species for the genus Ampelovirus, is regarded as the most important causative agent. Here we provide a general overview on various aspects of GLRaV-3, with an emphasis on the latest advances in the characterization of the genome. The full genome of several isolates have recently been sequenced and annotated, revealing the existence of several genetic variants. The classification of these variants, based on their genome sequence, will be discussed and a guideline is presented to facilitate future comparative studies. The characterization of sgRNAs produced during the infection cycle of GLRaV-3 has given some insight into the replication strategy and the putative functionality of the ORFs. The latest nucleotide sequence based molecular diagnostic techniques were shown to be more sensitive than conventional serological assays and although ELISA is not as sensitive it remains valuable for high-throughput screening and complementary to molecular diagnostics. The application of next-generation sequencing is proving to be a valuable tool to study the complexity of viral infection as well as plant pathogen interaction. Next-generation sequencing data can provide information regarding disease complexes, variants of viral species, and abundance of particular viruses. This information can be used to develop more accurate diagnostic assays. Reliable virus screening in support of robust grapevine certification programs remains the cornerstone of GLD management.

During the past two decades, onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), has become a global pest of increasing concern in commercial onion (Allium cepa L.), because of its development of resistance to insecticides, ability to transmit plant pathogens, and frequency of producing more generations at high temperatures. T. tabaci feeds directly on leaves, causing blotches and premature senescence as well as distorted and undersized bulbs. T. tabaci can cause yield loss Ͼ50% but can be even more problematic when it transmits Iris yellow spot virus (family Bunyaviridae, genus Tospovirus, IYSV). IYSV was identiÞed in 1981 in Brazil and has spread to many important onion-producing regions of the world, including several U.S. states. IYSV symptoms include straw-colored, dry, tan, spindle-or diamond-shaped lesions on the leaves and scapes of onion plants and can cause yield loss up to 100%. Here, we review the biology and ecology of T. tabaci and discuss current management strategies based on chemical, biological, and cultural control as well as host resistance. Future directions for research in integrated pest management are examined and discussed.RESUMEN En las ultimas dos dé cadas, el trips de la cebolla, Thrips tabaci Lindeman (Thysanoptera: Thripidae), se ha convertido en una plaga mundial de alto interé s en cebolla, Allium cepa L., debido a su desarrollo de resistencia a insecticidas, capacidad para transmitir pató genos en plantas, y producció n de mayor numero de generaciones a altas temperaturas. T. tabaci se alimenta directamente sobre las hojas causando manchas, senescencia prematura, asṍ como bulbos pequeñ os y desformados. T. tabaci puede causar perdidas en rendimiento mayores al 50%, pero esta plaga puede ser aun más problemática cuando transmite Iris yellow spot virus (family Bunyaviridae, genus Tospovirus, IYSV). IYSV fue identiÞcado en Brasil en 1981 y desde entonces se ha propagado a importantes regiones productoras de cebolla a nivel mundial, incluyendo diferentes estados en los Estados Unidos. Los sṍntomas del IYSV incluye lesiones secas en forma angular o de diamante, de color café claro en las hojas y tallos de la cebolla y puede producir hasta 100% de perdidas en rendimiento. En este articulo nosotros revisamos la biologṍa y ecologṍa de T. tabaci y presentamos los actuales mé todos de manejo basados en control quṍmico, bioló gico y cultural asṍ como el mé todo de resistencia de plantas a insectos. Las direcciones futuras para investigació n en manejo integrado de esta plaga son analizadas. KEY WORDS Thrips tabaci, Allium cepa, Iris yellow spot virus, managementOnion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), has been the subject of considerable research and extension publications since it was Þrst described in 1888 (Lindeman 1889). Some aspects of its biology, ecology, and management have been summarized in T. LewisÕ highly regarded 1997 book, Thrips as Crop Pests, but a considerable amount of detail important for its management on onion (Allium cepa L.)...

Grapevine (Vitis spp.) is one of the most widely grown fruit crops in the world. It is a deciduous woody perennial vine for which the cultivation of domesticated species began approximately 6,000 to 8,000 years ago in the Near East. Grapevines are broadly classified into red- and white-berried cultivars based on their fruit skin color, although yellow, pink, crimson, dark blue, and black-berried cultivars also exist. Grapevines can be subject to attacks by many different pests and pathogens, including graft-transmissible agents such as viruses, viroids, and phytoplasmas. Among the virus and virus-like diseases, grapevine leafroll disease (GLD) is by far the most widespread and economically damaging viral disease of grapevines in many regions around the world. The global expansion of the grape and wine industry has seen a parallel increase in the incidence and economic impact of GLD. Despite the fact that GLD was recognized as a potential threat to grape production for several decades, our knowledge of the nature of the disease is still quite limited due to a variety of challenges related to the complexity of this virus disease, the association of several distinct GLD-associated viruses, and contrasting symptoms in red- and white-berried cultivars. In view of the growing significance of GLD to wine grape production worldwide, this feature article provides an overview of the state of knowledge on the biology and epidemiology of the disease and describes management strategies currently deployed in vineyards.