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Loss of the awn in some cereals, including sorghum, is a key transition during cereal domestication or improvement that has facilitated grain harvest and storage. The genetic basis of awn loss in sorghum during domestication or improvement remains unknown. Here, we identified the awn1 gene encoding a transcription factor with the ALOG domain that is responsible for awn loss during sorghum domestication or improvement. awn1 arose from a gene duplication on chromosome 10 that translocated to chromosome 3, recruiting a new promoter from the neighboring intergenic region filled with “noncoding DNA” and recreating the first exon and intron. awn1 acquired high expression after duplication and represses the elongation of awns in domesticated sorghum. Comparative mapping revealed high collinearity at the awn1 paralog locus on chromosome 10 across cereals, and awn growth and development were successfully reactivated on the rice spikelet by inactivating the rice awn1 ortholog. RNA-seq and DAP-seq revealed that as a transcriptional repressor, AWN1 bound directly to a motif in the regulatory regions of three MADS genes related to flower development and two genes, DL and LKS2, involved in awn development. AWN1 downregulates the expression of these genes, thereby repressing awn elongation. The preexistence of regulatory elements in the neighboring intergenic region of awn1 before domestication implicates that noncoding DNA may serve as a treasure trove for evolution during sorghum adaptation to a changing world. Taken together, our results suggest that gene duplication can rapidly drive the evolution of gene regulatory networks in plants.

The complex gene regulatory network underlying tiller development in maize remains largely unknown. Here we identified two major quantitative trait loci for tiller number, Tin8 on chromosome 8 and the previously known Tb1 on chromosome 1, in a population derived from a teosinte–maize cross. Map-based cloning and association mapping revealed that Tin8, corresponding to Zcn8 encoding a phosphatidylethanolamine-binding-related kinase, is down-regulated in transcription, which results in decreased tiller number. A strong interaction between Tin8 and the key gen Tb1 was detected for tiller number. Further RNA-seq analysis showed that the expression of 13 genes related to tiller development was controlled by Tin8. Our results support the existence of a complex gene regulatory network for the outgrowth of the tiller bud in maize, in which Zcn8 controls 13 tiller-related genes, including four genes for hormonal responses. In particular, Zcn8 represses Gt1, D14, and Tru1 through the interaction with Tb1.

Loss of seed shattering was a key step during cereal domestication, and it greatly facilitated seed harvest of the staple cereal foxtail millet (Setaria italica) because the cereal has very small seeds. However, the genetic basis for this loss has been largely unknown. Here, we combined comparative and association mapping to identify an 855-bp Harbinger transposable element insertion in the second exon of the foxtail millet gene shattering1 (sh1) that was responsible for the loss of seed shattering. The sh1 gene encodes zinc finger and YABBY domains. The insert prevents transcription of the second exon, causing partial loss of the zinc finger domain and then loss of natural seed shattering. Specifically, sh1 functions as a transcription repressor and represses the transcription of genes associated with lignin synthesis in the abscission zone, including CAD2. The diversity of sh1 is highly reduced in foxtail millet, consistent with either a severe domestication bottleneck or a selective sweep. Phylogenetic analysis of sh1 further revealed a single origin of foxtail millet in China. Our results support the theories that transposons were the most active factors in genome evolution driving loss of natural seed shattering during foxtail millet domestication and that sh1 underwent parallel selection during domestication across different cereal species.

Loss of anthocyanin pigments is a common transition during cereal domestication, diversification, and improvement. However, the genetic basis for this convergent transition in cereal remains largely unknown. Here, we identified a chromosomal syntenic block across different species that contained R2R3-MYB genes (c1/pl1) responsible for the convergent decoloring of anthocyanins in cereals. Quantitative trait locus (QTL) mapping identified a major QTL for aerial root color corresponding to pl1 and a major QTL for spikelet color corresponding to c1 on maize chromosomes 6 and 9, respectively. One insertion in the regulatory region that led to transcriptional down-regulation was present in maize pl1, and several insertions in the coding region resulting in loss of function occurred in maize c1. A transposable element insertion in the third exon of c1, leading to three new non-functional transcripts, was responsible for decoloring in foxtail millet. The c1/pl1 genes enhanced the transcription of the core enzyme-encoding genes, including pr1, fht1, a1, a2, bz1, and aat1 in the anthocyanin pathway, while they repressed the expression of fnsii1 in flavones, sm2 in maysin, and bx3, bx4, bx5, and bx10 in DIMBOA. Our results indicated that the convergent decoloring of these plants shared the same genetic basis across different cereal species.

Sweet maize and popcorn retain tillering growth habit during maize diversification. However, the underlying molecular genetic mechanism remains unknown. Here, we show that the retention of maize tillering is controlled by a major quantitative trait locus (QTL), tin1, which encodes a C2H2-zinc-finger transcription factor that acts independently of tb1. In sweet maize, a splice-site variant from G/GT to C/GT leads to intron retention, which enhances tin1 transcript levels and consequently increases tiller number. Comparative genomics analysis and DNA diversity analysis reveal that tin1 is under parallel selection across different cereal species. tin1 is involved in multiple pathways, directly represses two tiller-related genes, gt1 and Laba1/An-2, and interacts with three TOPLESS proteins to regulate the outgrowth of tiller buds. Our results support that maize tin1, derived from a standing variation in wild progenitor teosinte population, determines tillering retention during maize diversification., Unlike the other domesticated maize, sweet maize and popcorn retain tillering growth habit, but the underlying mechanism is unknown. Here, the authors identify a transcription factor tin1 that maintains outgrowth of tiller independent of tb1 and show its conservation in foxtail millet and rice.

This paper proposes a bi-level decentralized active and reactive power control (DARPC) for the large-scale wind farm cluster (WFC) composed of several wind farms. The WFC tracks the active power reference from the transmission system operator (TSO) while controlling the bus voltage of the point of connection (POC), and maintaining the wind turbine (WT) terminal voltages stable in each wind farm. In the upper level, a distributed active and reactive power control scheme based on the consensus protocol is designed for the WFC, which can achieve fair active and reactive power sharing among multiple wind farms, and generates active and reactive power references for each wind farm. In the lower level, a centralized control scheme based on Model Predictive Control (MPC) is proposed, which can effectively regulates active and reactive power outputs of all WTs within the wind farm. The proposed centralized control scheme can maintain WTs terminal voltage close to the rated voltage while tracking the power reference from the upper level control. The DARPC can effectively reduce the computation burden of the WFC controller by distributing the computation and monitoring tasks to several wind farm controllers. Moreover, the communication cost is reduced. A WFC with 8 wind farms and totally 128 WTs was used to validate the proposed DARPC scheme.

To further improve the wind power quality and stability, it is necessary to break the existing open-loop wind farm scheduling method and bring new strategies in both wind farm and wind turbine active power control. In this paper, a closed-loop active power control method is proposed based on the active power tracking dynamic characteristics of wind turbines, where the power fluctuations caused by the modeling errors and wind turbulence are isolated and suppressed by a proportional-integral (PI) controller. The PI controller parameters are obtained through the frequency domain analysis with bode diagrams. Then a frequency-domain aggregation and approximation method is proposed to establish the wind farm active power tracking model, and the wind farm-level controller is obtained similarly with the unit-level one but with an event-driven integral structure. Simulation results show the significant improvement and good robustness of the proposed controller.

This paper proposes a decentralized coordinated voltage control scheme (DCVCS) for voltage-source-converter high voltage direct current (VSC-HVDC) connected wind farms based on the Model Predictive Control (MPC) which regulates the voltage profile across the wind farm network within the feasible range by optimally coordinating the VSC and wind turbines (WTs). Firstly, the centralized voltage control problem based on the MPC is formulated to minimize voltage deviations and reactive power output fluctuations of WTs. Secondly, the decentralized solution methodology based on Alternating Direction Method of Multipliers (ADMM) with fast convergency is used to solve the MPC problem in a decentralized manner without losing the optimality of the primal problem. A wind farm with 64 WTs was used to validate the effectiveness and optimality of the proposed DCVCS.