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Tomato yellow leaf curl virus (TYLCV) and its related begomoviruses cause fast-spreading diseases in tomato worldwide. How this virus induces diseases remains largely unclear. Here we report a noncoding RNA-mediated model to elucidate the molecular mechanisms of TYLCV-tomato interaction and disease development. The circular ssDNA genome of TYLCV contains a noncoding intergenic region (IR), which is known to mediate viral DNA replication and transcription in host cells, but has not been reported to contribute directly to viral disease development. We demonstrate that the IR is transcribed in dual orientations during plant infection and confers abnormal phenotypes in tomato independently of protein-coding regions of the viral genome. We show that the IR sequence has a 25-nt segment that is almost perfectly complementary to a long noncoding RNA (lncRNA, designated as SlLNR1) in TYLCV-susceptible tomato cultivars but not in resistant cultivars which contains a 14-nt deletion in the 25-nt region. Consequently, we show that viral small-interfering RNAs (vsRNAs) derived from the 25-nt IR sequence induces silencing of SlLNR1 in susceptible tomato plants but not resistant plants, and this SlLNR1 downregulation is associated with stunted and curled leaf phenotypes reminiscent of TYLCV symptoms. These results suggest that the lncRNA interacts with the IR-derived vsRNAs to control disease development during TYLCV infection. Consistent with its possible function in virus disease development, over-expression of SlLNR1 in tomato reduces the accumulation of TYLCV. Furthermore, gene silencing of the SlLNR1 in the tomato plants induced TYLCV-like leaf phenotypes without viral infection. Our results uncover a previously unknown interaction between vsRNAs and host lncRNA, and provide a plausible model for TYLCV-induced diseases and host antiviral immunity, which would help to develop effective strategies for the control of this important viral pathogen.

Archean cratons are the most stable tectonic units and their lithospheric mantle is chemically depleted and buoyant relative to the underlying mantle. The chemical depletion leads to high viscosity that maintains the long-term stability of cratons. However, the eastern part of the North China Craton ($1200 km in horizontal length scale) had been extensively reactivated and modified over a time scale of $100 Myr in the Mesozoic and Cenozoic. While the causes for the weakening of the North China Craton, a necessary condition for its reactivation, are still in debate, we investigate gravitational instability of compositionally buoyant lithosphere, by computing 2-D thermochemical convection models with different buoyancy number, lithospheric viscosity, and rheology. We find that the gravitational instability of cratonic lithosphere can happen over a larger range of buoyancy numbers with non-Newtonian rheology, but lithospheric instability with Newtonian rheology only happens with relatively small buoyancy numbers. For cratonic lithosphere with non-Newtonian rheology and relatively weak temperature-dependent viscosity, the instability starts in the cold, shallow part of the lithosphere and has small horizontal length scale (<300 km), leading to efficient thermal and chemical mixing with the underlying mantle. For cratonic lithosphere such as the eastern North China Craton, the instability process is episodic and consists of multiple instability events that may last for $100 Myr. The instability process revealed from our study explains the observations of episodic magmatism/volcanism events, geochemical mixing, and time scales associated with the reactivation of the North China Craton.

The method succeeds for indole derivatives equipped with electron‐donating substituents on the benzene ring, but fails with the electron‐withdrawing fluoro‐substituent.