Dynamic transcriptome landscape of maize pericarp development.

As a maternal tissue, the pericarp supports and protects for other components of seed, such as embryo and endosperm. Despite the importance of maize pericarp in seed, the genome-wide transcriptome pattern throughout maize pericarp development has not been well characterized. Here, we developed RNA-seq transcriptome atlas of B73 maize pericarp development based on 21 samples from 5 days before fertilization (DBP5) to 32 days after fertilization (DAP32). A total of 25 346 genes were detected in programming pericarp development, including 1887 transcription factors (TFs). Together with pericarp morphological changes, the global clustering of gene expression revealed four developmental stages: undeveloped, thickening, expansion and strengthening. Coexpression analysis provided further insights on key regulators in functional transition of four developmental stages. Combined with non-seed, embryo, endosperm, and nucellus transcriptome data, we identified 598 pericarp-specific genes, including 75 TFs, which could elucidate key mechanisms and regulatory networks of pericarp development. Cell wall related genes were identified that reflected their crucial role in the maize pericarp structure building. In addition, key maternal proteases or TFs related with programmed cell death (PCD) were proposed, suggesting PCD in the maize pericarp was mediated by vacuolar processing enzymes (VPE), and jasmonic acid (JA) and ethylene-related pathways. The dynamic transcriptome atlas provides a valuable resource for unraveling the genetic control of maize pericarp development.

Maize sterility gene DRP1 encodes a desiccation-related protein that is critical for Ubisch bodies and pollen exine development.

Desiccation tolerance is a remarkable feature of pollen, seeds, and resurrection-type plants. Exposure to desiccation stress can cause sporophytic defects, resulting in male sterility. Here, we report the novel maize sterility gene DRP1 (Desiccation-Related Protein 1), which was identified by bulked-segregant analysis sequencing and encodes a desiccation-related protein. Loss of function of DRP1 results in abnormal Ubisch bodies, defective tectum of the pollen exine, and complete male sterility. Our results suggest that DRP1 may facilitate anther dehydration to maintain appropriate water status. DRP1 is a secretory protein that is specifically expressed in the tapetum and microspore from the tetrad to the uninucleate microspore stage. Differentially expressed genes in drp1 are enriched in Gene Ontology terms for pollen exine formation, polysaccharide catabolic process, extracellular region, and response to heat. In addition, DRP1 is a target of selection that appears to have played an important role in the spread of maize from tropical/subtropical to temperate regions. Taken together, our results suggest that DRP1 encodes a desiccation-related protein whose loss of function causes male sterility. Our findings provide a potential genetic resource that may be used to design crops for heterosis utilization.

Exploring key developmental phases and phase-specific genes across the entirety of anther development in maize.

Anther development from stamen primordium to pollen dispersal is complex and essential to sexual reproduction. How this highly dynamic and complex developmental process is controlled genetically is not well understood, especially for genes involved in specific key developmental phases. Here we generated RNA sequencing libraries spanning 10 key stages across the entirety of anther development in maize (Zea mays). Global transcriptome analyses revealed distinct phases of cell division and expansion, meiosis, pollen maturation, and mature pollen, for which we detected 50, 245, 42, and 414 phase-specific marker genes, respectively. Phase-specific transcription factor genes were significantly enriched in the phase of meiosis. The phase-specific expression of these marker genes was highly conserved among the maize lines Chang7-2 and W23, indicating they might have important roles in anther development. We explored a desiccation-related protein gene, ZmDRP1, which was exclusively expressed in the tapetum from the tetrad to the uninucleate microspore stage, by generating knockout mutants. Notably, mutants in ZmDRP1 were completely male-sterile, with abnormal Ubisch bodies and defective pollen exine. Our work provides a glimpse into the gene expression dynamics and a valuable resource for exploring the roles of key phase-specific genes that regulate anther development.

ZmCTLP1 is required for the maintenance of lipid homeostasis and the basal endosperm transfer layer in maize kernels.

Maize kernel weight is influenced by the unloading of nutrients from the maternal placenta and their passage through the transfer tissue of the basal endosperm transfer layer (BETL) and the basal intermediate zone (BIZ) to the upper part of the endosperm. Here, we show that Small kernel 10 (Smk10) encodes a choline transporter-like protein 1 (ZmCTLP1) that facilitates choline uptake and is located in the trans-Golgi network (TGN). Its loss of function results in reduced choline content, leading to smaller kernels with a lower starch content. Mutation of ZmCTLP1 disrupts membrane lipid homeostasis and the normal development of wall in-growths. Expression levels of Mn1 and ZmSWEET4c, two kernel filling-related genes, are downregulated in the smk10, which is likely to be one of the major causes of incompletely differentiated transfer cells. Mutation of ZmCTLP1 also reduces the number of plasmodesmata (PD) in transfer cells, indicating that the smk10 mutant is impaired in PD formation. Intriguingly, we also observed premature cell death in the BETL and BIZ of the smk10 mutant. Together, our results suggest that ZmCTLP1-mediated choline transport affects kernel development, highlighting its important role in lipid homeostasis, wall in-growth formation and PD development in transfer cells.

Cloning and Characterization of TaTGW-7A Gene Associated with Grain Weight in Wheat via SLAF-seq-BSA.

Thousand-grain weight (TGW) of wheat (Triticum aestivum L.) contributes significantly to grain yield. In the present study, a candidate gene associated with TGW was identified through specific-locus amplified fragment sequencing (SLAF-seq) of DNA bulks of recombinant inbred lines (RIL) derived from the cross between Jing 411 and Hongmangchun 21. The gene was located on chromosome 7A, designated as TaTGW-7A with a complete genome sequence and an open reading frame (ORF). A single nucleotide polymorphism (SNP) was present in the first exon between two alleles at TaTGW-7A locus, resulting in a Val to Ala substitution, corresponding to a change from higher to lower TGW. Cleaved amplified polymorphic sequence (CAPS) (TGW7A) and InDel (TG9) markers were developed to discriminate the two alleles TaTGW-7Aa and TaTGW-7Ab for higher and lower TGW, respectively. A major QTL co-segregating with TaTGW-7A explained 21.7-27.1% of phenotypic variance for TGW in the RIL population across five environments. The association of TaTGW-7A with TGW was further validated in a natural population and Chinese mini-core collections. Quantitative real-time PCR revealed higher transcript levels of TaTGW-7Aa than those of TaTGW-7Ab during grain development. High frequencies of the superior allele TaTGW-7Aa for higher TGW in Chinese mini-core collections (65.0%) and 501 wheat varieties (86.0%) indicated a strong and positive selection of this allele in wheat breeding. The molecular markers TGW7A and TG9 can be used for improvement of TGW in breeding programs.

[Early clinical outcome of manual reduction combined with uni-lateral percutaneous kyphoplasty to treat osteoporotic vertebral compression fracture].

OBJECTIVE: To investigate the efficiency of manual reduction combined with uni-lateral percutaneous kyphoplasty (PKP) in treating osteoporotic vertebral compression fracture (OVCF). METHODS: Between May 2005 and May 2009, the manual reduction combined with uni-lateral PKP was applied to treat 42 patients with OVCF (group A), and the simple uni-lateral PKP was applied to treat 43 patients with OVCF (group B) at the same period. The visual analogue scale (VAS), the vertebral height, and the Cobb angle were determined before operation, and at 3 days and 6 months after operation. In group A, there were 6 males and 36 females aged 59-93 years (76.5 years on average) with an average disease duration of 7 days (range, 3 hours to 21 days); 27 segments of thoracic vertebrae and 31 segments of lumbar vertebrae were involved, including 15 segments at mild degree, 38 segments at moderate degree, and 5 segments at severe degree according to degree classification system of compression fractures of Zoarski and Peh. In group B, there were 9 males and 34 females aged 54-82 years (75.3 years on average) with an average disease duration of 7 days (range, 1 hour to 20 days); 26 segments of thoracic vertebrae and 35 segments of lumbar vertebrae were involved, including 21 segments at mild degree, 36 segments at moderate degree, and 4 segments at severe degree according to degree classification system of compression fractures of Zoarski and Peh. There were no significant difference (P > 0.05) in sex, age, affected site, degree, and disease duration between 2 groups. RESULTS: There was no significant difference (P > 0.05) in operative time, blood loss, or injected cement volume between 2 groups. No serious complication or death occurred in 2 groups. Cement leakage was observed in 4 cases (9.5%) of group A and in 5 cases (11.6%) of group B. The VAS scores after operation significantly decreased in 2 groups (P < 0.01). At 3 days and 6 months after operation, the VAS scores in group A were significantly lower than those in group B (P < 0.05). The postoperative compression rates of affected vertebral body in 2 groups significantly decreased (P < 0.01). The compression rates of affected vertebral body at 3 days and 6 months after operation, and the height recovery rate at 3 days after operation in group A were superior to those in group B (P < 0.05). The postoperative Cobb angles in 2 groups were significantly diminished (P < 0.01). The Cobb angles at 3 days and 6 months after operation, and the recovery rate at 3 days after operation in group A were superior to those in group B (P < 0.05). CONCLUSION: The clinical efficiency of the manual reduction combined with unilateral PKP is superior to that of simple uni-lateral PKP in treatment of severe OVCF.