Estimation of soil health in the semi­arid regions of northwestern Iran using digital elevation model and remote sensing data.

Nowadays, neglecting soil conservation issues is one of the most critical factors in reducing soil health (SH). In this regard, to facilitate the estimation of the SH in northwestern Iran, 292 soil samples were taken from a depth of 0-30 cm of this area, and a wide range of soil properties were determined. Then, soil health indices (SHIs) were calculated. Simultaneously, the normalized difference vegetation index (NDVI), surface water capacity index (SWCI), and a digital elevation model (DEM) were obtained from satellite data. Finally, multiple linear regression (MLR) relationships between these parameters and SHIs were calculated. In this study, there was a highest significant positive correlation (P < 0.01) between IHI-LTDS and SWCI (0.71**), DEM (0.76**), and NDVI (0.73**). The MLR, with both the whole total (TDS) and minimal (MDS) dataset methods, which includes the aforementioned indices, strongly described the spatial variability of the Integrated Soil Health Index (IHI) (R2 = 0.78, AIC = - 416, RMSE = 0.05, and ρc = 0.76). According to the results of this study, it can be said that the development of SH estimation models using remote sensing extracted parameters can be one of the effective ways to reduce the cost and time of soil sampling in extensive areas.

Metabolic Engineering of Wheat Provitamin A by Simultaneously Overexpressing CrtB and Silencing Carotenoid Hydroxylase (TaHYD).

Increasing the provitamin A content in staple crops via carotenoid metabolic engineering is one way to address vitamin A deficiency. In this work a combination of methods was applied to specifically increase ß-carotene content in wheat by metabolic engineering. Endosperm-specific silencing of the carotenoid hydroxylase gene (TaHYD) increased ß-carotene content 10.5-fold to 1.76 µg g(-1) in wheat endosperm. Overexpression of CrtB introduced an additional flux into wheat, accompanied by a ß-carotene increase of 14.6-fold to 2.45 µg g(-1). When the "push strategy" (overexpressing CrtB) and "block strategy" (silencing TaHYD) were combined in wheat metabolic engineering, significant levels of ß-carotene accumulation were obtained, corresponding to an increase of up to 31-fold to 5.06 µg g(-1). This is the first example of successful metabolic engineering to specifically improve ß-carotene content in wheat endosperm through a combination of methods and demonstrates the potential of genetic engineering for specific nutritional enhancement of wheat.

The lycopene ß-cyclase plays a significant role in provitamin A biosynthesis in wheat endosperm.

BACKGROUND: Lycopene ß-cyclase (LCYB) is a key enzyme catalyzing the biosynthesis of ß-carotene, the main source of provitamin A. However, there is no documented research about this key cyclase gene's function and relationship with ß-carotene content in wheat. Therefore, the objectives of this study were to clone TaLCYB and characterize its function and relationship with ß-carotene biosynthesis in wheat grains. We also aimed to obtain more information about the endogenous carotenoid biosynthetic pathway and thus provide experimental support for carotenoid metabolic engineering in wheat. RESULTS: In the present study, a lycopene ß-cyclase gene, designated TaLCYB, was cloned from the hexaploid wheat cultivar Chinese Spring. The cyclization activity of the encoded protein was demonstrated by heterologous complementation analysis. The TaLCYB gene was expressed differentially in different tissues of wheat. Although TaLCYB had a higher expression level in the later stages of grain development, the ß-carotene content still showed a decreasing tendency. The expression of TaLCYB in leaves was dramatically induced by strong light and the ß-carotene content variation corresponded with changes of TaLCYB expression. A post-transcriptional gene silencing strategy was used to down-regulate the expression of TaLCYB in transgenic wheat, resulting in a decrease in the content of ß-carotene and lutein, accompanied by the accumulation of lycopene to partly compensate for the total carotenoid content. In addition, changes in TaLCYB expression also affected the expression of several endogenous carotenogenic genes to varying degrees. CONCLUSION: Our results suggest that TaLCYB is a genuine lycopene cyclase gene and plays a crucial role in ß-carotene biosynthesis in wheat. Our attempt to silence it not only contributes to elucidating the mechanism of carotenoid accumulation in wheat but may also help in breeding wheat varieties with high provitamin A content through RNA interference (RNAi) to block specific carotenogenic genes in the wheat endosperm.

Enrichment of provitamin A content in wheat (Triticum aestivum L.) by introduction of the bacterial carotenoid biosynthetic genes CrtB and CrtI.

Carotenoid content is a primary determinant of wheat nutritional value and affects its end-use quality. Wheat grains contain very low carotenoid levels and trace amounts of provitamin A content. In order to enrich the carotenoid content in wheat grains, the bacterial phytoene synthase gene (CrtB) and carotene desaturase gene (CrtI) were transformed into the common wheat cultivar Bobwhite. Expression of CrtB or CrtI alone slightly increased the carotenoid content in the grains of transgenic wheat, while co-expression of both genes resulted in a darker red/yellow grain phenotype, accompanied by a total carotenoid content increase of approximately 8-fold achieving 4.76 µg g(-1) of seed dry weight, a ß-carotene increase of 65-fold to 3.21 µg g(-1) of seed dry weight, and a provitamin A content (sum of α-carotene, ß-carotene, and ß-cryptoxanthin) increase of 76-fold to 3.82 µg g(-1) of seed dry weight. The high provitamin A content in the transgenic wheat was stably inherited over four generations. Quantitative PCR analysis revealed that enhancement of provitamin A content in transgenic wheat was also a result of the highly coordinated regulation of endogenous carotenoid biosynthetic genes, suggesting a metabolic feedback regulation in the wheat carotenoid biosynthetic pathway. These transgenic wheat lines are not only valuable for breeding wheat varieties with nutritional benefits for human health but also for understanding the mechanism regulating carotenoid biosynthesis in wheat endosperm.