14-3-3 proteins contribute to autophagy by modulating SINAT-mediated degradation of ATG13.

In multicellular eukaryotes, autophagy is a conserved process that delivers cellular components to the vacuole or lysosome for recycling during development and stress responses. Induction of autophagy activates AUTOPHAGY-RELATED PROTEIN 1 (ATG1) and ATG13 to form a protein kinase complex that initiates autophagosome formation. However, the detailed molecular mechanism underlying the regulation of this protein complex in plants remains unclear. Here, we determined that in Arabidopsis thaliana, the regulatory proteins 14-3-3λ and 14-3-3κ redundantly modulate autophagy dynamics by facilitating SEVEN IN ABSENTIA OF ARABIDOPSIS THALIANA (SINAT)-mediated proteolysis of ATG13a and ATG13b. 14-3-3λ and 14-3-3κ directly interacted with SINATs and ATG13a/b in vitro and in vivo. Compared to wild-type (WT), the 14-3-3λ 14-3-3κ double mutant showed increased tolerance to nutrient starvation, delayed leaf senescence, and enhanced starvation-induced autophagic vesicles. Moreover, 14-3-3s were required for SINAT1-mediated ubiquitination and degradation of ATG13a. Consistent with their roles in ATG degradation, the 14-3-3λ 14-3-3κ double mutant accumulated higher levels of ATG1a/b/c and ATG13a/b than the WT upon nutrient deprivation. Furthermore, the specific association of 14-3-3s with phosphorylated ATG13a was crucial for ATG13a stability and formation of the ATG1-ATG13 complex. Thus, our findings demonstrate that 14-3-3λ and 14-3-3κ function as molecular adaptors to regulate autophagy by modulating the homeostasis of phosphorylated ATG13.

A viral protein orchestrates rice ethylene signaling to coordinate viral infection and insect vector-mediated transmission.

Arthropod-borne viruses cause serious threats to human health and global agriculture by rapidly spreading via insect vectors. Southern rice black-streaked dwarf virus (SRBSDV) is the most damaging rice-infecting virus that is frequently transmitted by planthoppers. However, the molecular mechanisms underlying its propagation in the host plants and epidemics in the field are largely unknown. Here, we showed that the SRBSDV-encoded P6 protein is a key effector that regulates rice ethylene signaling to coordinate viral infection and transmission. In early SRBSDV infection, P6 interacts with OsRTH2 in the cytoplasm to activate ethylene signaling and enhance SRBSDV proliferation; this also repels the insect vector to reduce infestation. In late infection, P6 enters the nucleus, where it interacts with OsEIL2, a key transcription factor of ethylene signaling. The P6-OsEIL2 interaction suppresses ethylene signaling by preventing the dimerization of OsEIL2, thereby facilitating viral transmission by attracting the insect vector. Collectively, these findings reveal a novel molecular mechanism by which an arbovirus modulates the host defense system to promote viral infection and transmission.

Resistance Evaluation of Dominant Varieties against Southern Rice Black-Streaked Dwarf Virus in Southern China.

Southern rice black-streaked dwarf virus (SRBSDV), a Fijivirus in the Reoviridae family, is transmitted by the white-backed planthopper (Sogatella furcifera, WBPH), a long-distance migratory insect, and presents a serious threat to rice production in Asia. It was first discovered in China's Guangdong Province in 2001 and has been endemic in the south of China and north of Vietnam for two decades, with serious outbreaks in 2009, 2010, and 2017. In this study, we evaluated the resistance of 10 dominant rice varieties from southern China, where the virus overwinters and accumulates as a source of early spring reinfection, against this virus by artificial inoculation. The results showed that in all tested varieties there was no immune resistance, but there were differences in the infection rate, with incidence rates from 21% to 90.7%, and in symptom severity, with plant weight loss from 66.71% to 91.20% and height loss from 34.1% to 65.06%. Additionally, and valuably, the virus titer and the insect vector virus acquisition potency from diseased plants were significantly different among the varieties: an over sixfold difference was determined between resistant and susceptible varieties, and there was a positive correlation between virus accumulation and insect vector virus acquisition. The results can provide a basis for the selection of rice varieties in southern China to reduce the damage of SRBSDV in this area and to minimize the reinfection source and epidemics of the virus in other rice-growing areas.