The B-Type Cyclin CYCB1-1 Regulates Embryonic Development and Seed Size in Maize.

Progress through the cell cycle is a critical process during plant embryo and seed development and its progression is regulated by cyclins. Despite extensive study of cyclins in other systems, their role in embryo and seed development of maize is unclear. In this study, we demonstrate that ZmCYCB1-1 overexpression significantly accelerated embryo growth and increased seed size. In situ hybridization and toluidine blue staining indicated that ZmCYCB1-1 was highly expressed in the plumule of embryos, and the cells of the plumule were smaller, denser, and more regularly arranged in ZmCYCB1-1 overexpression plants. Overexpression of ZmCYCB1-1 in maize also resulted in an increased ear length and enhanced kernel weight by increasing kernel width. Transcriptome analysis indicated that the overexpression of ZmCYCB1-1 affected several different metabolic pathways, including photosynthesis in embryos and leaves, and lipid metabolism in leaves. Conversely, knocking out ZmCYCB1-1 resulted in plants with slow growth. Our results suggest that ZmCYCB1-1 regulates embryo growth and seed size, making it an ideal target for efforts aimed at maize yield improvement.

iTRAQ-based quantitative proteomic analysis provides insight into the drought-stress response in maize seedlings.

Drought is a major abiotic stress that harms plant cell physiology and limits the growth and productivity of crops. Maize (Zea mays L.), one of the most drought-susceptible crops, is a major food source for humans and an important resource for industrial bioenergy production; therefore, understanding the mechanisms of the drought response is essential for maize improvement. Using isotopic tagging relative quantitation (iTRAQ)-based protein labeling technology, we detected the proteomic changes in maize leaves under drought stress. Among the 3063 proteins that were identified, the abundance of 214 and 148 proteins increased and decreased, respectively, after three days of drought treatment. These differentially abundant proteins (DAPs) were mainly involved in cell redox homeostasis, cell wall organization, photosynthesis, abscisic acid biosynthesis, and stress-response processes. Furthermore, some of the DAP abundances still differed from the control six days after the drought treatment, most of which were molecular chaperones, heat shock proteins, metabolism-related enzymes, hydrolases, and transmembrane signal receptors. The expression level of some DAPs returned to normal when the water supply was restored, but for others it did not. A significant correlation between the protein and transcript levels was observed following an RT-qPCR analysis. Finally, our research provides insights into the overall mechanism of drought-stress tolerance, and important information for breeding of drought-tolerant maize.

Comprehensive analysis of MAPK cascade genes in sorghum (Sorghum bicolor L.) reveals SbMPK14 as a potential target for drought sensitivity regulation.

The mitogen-activated protein kinase (MAPK) cascade plays a crucial role in regulating many important biological processes in plants. Here, we identified and characterized eight MAPKK and 49 MAPKKK genes in sorghum and analyzed their differential expression under drought treatment; we also characterized 16 sorghum MAPK genes. RNA-seq analysis revealed that 10 MAPK cascade genes were involved in drought stress response at the transcriptome level in sorghum. Overexpression of SbMPK14 in Arabidopsis and maize resulted in hypersensitivity to drought by promoting water loss, indicating that SbMPK14 functions as a negative regulator of the drought response. Subsequent transcriptome analysis and qRT-PCR verification of maize SbMPK14 overexpression lines revealed that SbMPK14 likely increases plant drought sensitivity by suppressing the activity of specific ERF and WRKY transcription factors. This comprehensive study provides valuable insight into the mechanistic basis of MAPK cascade gene function and their responses to drought in sorghum.

A leucine-rich repeat-receptor-like kinase gene SbER2-1 from sorghum (Sorghum bicolor L.) confers drought tolerance in maize.

BACKGROUND: ERECTA (ER) is a leucine-rich repeat-receptor-like kinase gene (LRR-RLK) encoding a protein isolated from Arabidopsis. Although the regulatory functions of ER genes have been widely explored in plant development and disease resistance, their roles in drought stress responses remain to be clarified. RESULTS: In this study, we cloned and characterized two ER genes, SbER1-1 and SbER2-1, from the drought-tolerant model plant sorghum (Sorghum bicolor L.). Under drought stress, the two genes were expressed in the leaves and stems but not in the roots, and SbER2-1 transcript accumulation in the stem was increased. SbER2-1 was localized both on the plasma membrane and in the chloroplast. Moreover, SbER2-1 expression in Arabidopsis and maize conferred increased drought tolerance, especially in regard to water-use efficiency, increasing the net photosynthetic rate in maize under drought stress. Based on RNA-Seq analysis together with the physiological data, we conclude that the transgenic maize plants have upregulated phenylpropanoid metabolism and increased lignin accumulation under drought stress. CONCLUSIONS: Our results demonstrate that SbER2-1 plays an important role in response to drought stress. Furthermore, photosynthetic systems and phenylpropanoid metabolism are implicated in SbER2-1-mediated drought stress tolerance mechanisms. The use of genetic engineering to regulate SbER2-1 expression in plants and to breed new varieties tolerant to drought is a research field full of potential.