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To explore the possible novel microRNA (miRNA) regulatory pathways in Zhengmai 1860, a newly cultivated drought-tolerant wheat (Triticum aestivum L.) cultivar, miRNA transcriptome sequencing of the flag leaves of Zhengmai 1860, drought-sensitive variety Zhoumai 18, and drought-resistant variety Bainong 207 was performed during the grain filling stage. We also observed changes in the chloroplast ultrastructure, phytohormone levels, and antioxidant- and photosynthesis-related physiological indicators in three wheat varieties. The results showed that the flag leaves of the drought-tolerant variety Zhengmai 1860 had higher chlorophyll contents and net photosynthetic rates than those of Zhoumai 18 under drought stress during the grain filling stage; in addition, the chloroplast structure was more complete. However, there was no significant difference between Zhengmai 1860 and Bainong 207. MiRNA transcriptome analysis revealed that the differential expression of the miRNAs and mRNAs exhibited variable specificity. The KEGG pathway enrichment results indicated that most of the genes were enriched in the MAPK signaling pathway, plant hormone signal transduction, photosynthetic antennae protein, and amino acid and carbohydrate metabolism. In the drought-tolerant cultivar Zhengmai 1860, tae-miR408 was targeted to regulate the allene oxide synthase (AOS) gene, inhibit its expression, reduce the AOS content, and decrease the synthesis of jasmonic acid (JA) and abscisic acid (ABA). The results of this study suggest that Zhengmai 1860 could improve the photosynthetic performance of flag leaves by inhibiting the expression of genes involved in the JA pathway through miRNAs under drought conditions. Moreover, multiple miRNAs may target chlorophyll, antioxidant enzymes, phytohormone signal transduction, and other related pathways; thus, it is possible to provide a more theoretical basis for wheat molecular breeding. [ABSTRACT FROM AUTHOR]

Psb28 is a soluble protein in the photosystem II (PSII) complex, but its role in the drought stress response of wheat remains unclear. Here, we functionally characterized the TaPsb28 gene, which positively regulates drought tolerance in wheat. When the full-length 546-bp TaPsb28 cDNA was transferred into Arabidopsis thaliana, it was located in the guard cell chloroplast around the stroma. Overexpression of TaPsb28 conferred drought tolerance, as exhibited by the increases in the survival rate. Transgenic plants maintained lower MDA content and higher chlorophyll content by inducing chlorophyll synthase (ChlG) gene transcription. The content of abscisic acid (ABA) and zeatin increased significantly in wild-type (WT) plants under drought stress, and the transcriptional expression levels of RD22, dihydroflavonol 4-reductase (DFR) and anthocyanin reductase (ANR) genes were induced, thus enhancing the contents of endogenous cyanidin, delphinidin, and proanthocyanidins. However, in transgenic plants, although anthocyanins were further aggregated, the ABA increase was inhibited, zeatin was restored to the control level under drought stress, and stomatal closure was promoted. These findings indicate ABA and zeatin have opposite synergistic effects in the process of drought tolerance caused by TaPsb28 because only after the effect of zeatin is alleviated can ABA better play its role in promoting anthocyanin accumulation and stomatal closure, thus enhancing the drought tolerance of transgenic plants. The results suggest that overexpression of TaPsb28 exerts a positive role in the drought response by influencing the functional metabolism of endogenous hormones. The understanding acquired through the research laid a foundation for further in-depth investigation of the function of TaPsb28 in drought resistance in wheat, especially its relationship with anthocyanidin accumulation. [ABSTRACT FROM AUTHOR]

Summary: Genetically enhancing drought tolerance and nutrient use efficacy enables sustainable and stable wheat production in drought‐prone areas exposed to water shortages and low soil fertility, due to global warming and declining natural resources. In this study, wheat plants, exhibiting improved drought tolerance and N‐use efficacy, were developed by introducing GmTDN1, a gene encoding a DREB‐like transcription factor, into two modern winter wheat varieties, cv Shi4185 and Jimai22. Overexpressing GmTDN1 in wheat resulted in significantly improved drought and low‐N tolerance under drought and N‐deficient conditions in the greenhouse. Field trials conducted at three different locations over a period of 2–3 consecutive years showed that both Shi4185 and Jimai22 GmTDN1 transgenic lines were agronomically superior to wild‐type plants, and produced significantly higher yields under both drought and N‐deficient conditions. No yield penalties were observed in these transgenic lines under normal well irrigation conditions. Overexpressing GmTDN1 enhanced photosynthetic and osmotic adjustment capacity, antioxidant metabolism, and root mass of wheat plants, compared to those of wild‐type plants, by orchestrating the expression of a set of drought stress‐related genes as well as the nitrate transporter, NRT2.5. Furthermore, transgenic wheat with overexpressed NRT2.5 can improve drought tolerance and nitrogen (N) absorption, suggesting that improving N absorption in GmTDN1 transgenic wheat may contribute to drought tolerance. These findings may lead to the development of new methodologies with the capacity to simultaneously improve drought tolerance and N‐use efficacy in cereal crops to ensure sustainable agriculture and global food security. [ABSTRACT FROM AUTHOR]

Using particle bombardment transformation, we introduced maize pepc cDNA encoding phosphoenolpyruvate carboxylase (PEPC) and ppdk cDNA encoding pyruvate orthophosphate dikinase (PPDK) into the C crop wheat to generate transgenic wheat lines carrying cDNA of pepc (PC lines), ppdk (PK lines) or both (PKC lines). The integration, transcription, and expression of the foreign genes were confirmed by Southern blot, Real-time quantitative reverse transcription PCR (Q-RT-PCR), and Western blot analysis. Q-RT-PCR results indicated that the average relative expression levels of pepc and ppdk in the PKC lines reached 10 and 4.6, respectively, compared to their expressions in untransformed plants (set to 1). The enzyme activities of PEPC and PPDK in the PKC lines were 4.3- and 2.1-fold higher, respectively, than in the untransformed control. The maximum daily net photosynthetic rates of the PKC, PC, and PK lines were enhanced by 26.4, 13.3, and 4.5 %, respectively, whereas the diurnal accumulations of photosynthesis were 21.3, 13.9, and 6.9 %, respectively, higher than in the control. The F/F of the transgenic plants decreased less than in the control under high temperature and high light conditions (2 weeks after anthesis), suggesting that the transgenic wheat transports more absorbed light energy into a photochemical reaction. The exogenous maize C-specific pepc gene was more effective than ppdk at improving the photosynthetic performance and yield characteristics of transgenic wheat, while the two genes showed a synergistic effect when they were transformed into the same genetic background, because the PKC lines exhibited improved photosynthetic and physiological traits. [ABSTRACT FROM AUTHOR]

With 7 figures and 2 tables Abstract Attempts have been made to transform C3 crops with C4 genes to improve the photosynthetic rate of C3 plants. In our study, a full-length cDNA for phosphoenolpyruvate carboxylase gene ( pepc) was isolated from Zea mays by PCR. The pepc gene was introduced into wheat plants ( Triticum aestivum) by particle bombardment transformation. The integration, transcription and expression of the pepc gene were confirmed by Southern blot, RT-PCR and Western blot analysis. Physiological studies showed that phosphoenolpyruvate carboxylase activity in the transgenic plants was 140% higher than that of the untransformed plants. The highest rate of photosynthesis in the transgenic plants was 31.95 μmol CO2/m2/s, which was 26% greater than the rate in untransformed plants. The light saturation point and carboxylation efficiency of pepc transgenic wheat were 20% and 22.57% higher, respectively, than those of untransformed wheat. As a result, the weight of seed per spike and thousand-grain weight were 0.23 g and 1.21 g higher than those of untransformed wheat. Our research will facilitate the further study of the function of the pepc gene in wheat plants. [ABSTRACT FROM AUTHOR]

Wheat is one of the staple food crops worldwide and breeding for high yield wheat is critical to meet the need of increasing world population. To determine the factors that limit wheat yield potential in Henan province, China, 30 wheat cultivars that have been widely grown in Henan province since 1940s were evaluated for grain yield and related physiological traits. The results show that grain yield has been significantly increased since 1940s, with an annual genetic gain of 1.09%, and the increased yield after 1900s was attributed to the introduction of 1BL/1RS translocation. The significant yield increase mainly resulted from a significant increase in grain number per spike (GNPS), thousand kernel weight (TKW) and harvest index (HI), and a significant decrease in plant height due to utilization of semi-dwarfing genes. The genetic improvement of assimilate accumulation and translocation was mainly reflected by the improvement in post-anthesis assimilate accumulation (PoAAA) and post-anthesis transportion rate (PoATR) of pre-anthesis assimilates (PrAA), with genetic gains of 0.63% and 1.89%, respectively. The improvement of the PoAAA was closely related to an increase in net photosynthetic rates ( P n ) of flag leaves at anthesis and 20 days after anthesis, and leaf area index (LAI) at 20 days after anthesis; whereas the improvement of the PoATR of the PrAA was closely associated with the improvement of accumulation and redistribution of the assimilates accumulated in stems and sheaths. As yield increased, the source-sink ratio significantly decreased, reflecting that the source has been gradually becoming a limiting factor to grain yield increase. Therefore, diverse strategies should be adopted to improve biomass (source) in future wheat breeding to meet the need of continuous increasing in wheat yield. [ABSTRACT FROM AUTHOR]