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Auxin is an important endogenous hormone in plants. The YUCCA gene encodes a flavin monooxygenase, which is an important rate-limiting enzyme in the auxin synthesis pathway and involved in the regulation of plant growth and development. In the study, we identified 63 wheat TaYUCCA genes; among them, some genes appeared in clusters. By constructing phylogenetic trees, we found that the TaYUCCA genes could be divided into six groups. In the WheatExp database, there were 22 differential expressed TaYUCCA genes, among which the TaYUCCA10 gene was abundantly expressed in the endosperm and medium milk stage, the TaYUCCA2 gene was abundantly expressed in the roots of three leaves and meiosis and transfer cells at 20 days post anthesis and the others 16 TaYUCCA genes had different expression level at different developmental stages in wheat, and there were 15 TaYUCCA genes induced by drought and heat stress, among which the TaYUCCA2-D, TaYUCCA3-B, and TaYUCCA9-D might be upregulated induced by drought stress, TaYUCCA10.1 might be upregulated induced drought and heat stress, TaYUCCA6-A was upregulated induced both drought and heat stress and the others 9 TaYUCCA genes were downregulated induced by drought and heat stress. Transcriptome and qRT-PCR analysis showed that TaYUCCA7-A was upregulated significantly after induced by powdery mildew. The comprehensive annotation and expression profiling of the TaYUCCA genes in this study enhanced our understanding of TaYUCCA family gene expression in wheat growth and development and laid the foundation for the further study of TaYUCCA gene mechanism.

Key Message: Present study revealed that specific expression of TaYUC10.3 in wheat young seeds could increase the content of auxin, and protein. Auxin is a vital endogenous hormone in plants, which is involved in the regulation of various physiological and biochemical processes in plants. The flavin-containing monooxygenase encoded by the YUCCA gene is a rate-limiting enzyme in the tryptophan-dependent pathway of auxin synthesis. TaYUC10.3 was identified, cloned and found that it was abundantly expressed in wheat young seeds. In this study, a seed-specific expression vector of TaYUC10.3 was constructed with the promoter of 1Bx17 glutenin subunit gene and transformed wheat using the particle bombardment method. The quantitative RT-PCR showed that TaYUC10.3 was expressed in a large amount in young seeds of the transgenic lines. Plant hormone-targeted metabolomics showed that the auxin content of the transgenic lines was significantly increased compared with controls. The GC / MS non-targeted metabolite multiple statistical analyses showed that the variable importance in projection (VIP) of tryptophan reduced in the transgenic lines. Simultaneously, the VIP of indole acetic acid increased. The precursor amino acids for synthesizing some proteins and carbohydrates were upregulated in the transgenic lines. Subsequently, it was found that the protein content of the seeds of the transgenic TaYUC10.3 wheat was significantly higher than that of the control. The wet gluten content and sedimentation value of the transgenic TaYUC10.3 wheat were also high. This result indicated that TaYUC10.3 might participate in auxin synthesis and affects the protein content of wheat seeds.

Aspartic proteases (APs) are one of the four main protease super families. In plants, they are involved in many biological processes, such as biotic and abiotic stress resistance, protein processing and degradation, senescence, and programmed cell death. By performing a database (TGACv1) search and domain prediction, we identified 263 wheat AP (TaAP) proteins and observed 38 TaAP genes exhibiting alternative splicing. Moreover, by constructing a phylogenetic tree, we found that the TaAP proteins can be divided into three families and have a certain close evolutionary relationship to Arabidopsis thaliana and rice AP proteins. Transcriptome analysis showed that 29 genes in the TaAP family were up-regulated after being induced by powdery mildew. The expression of TaAP224 showed the most significant difference in transcriptome and qRT-PCR analyses. Subsequently, the promoters of these 29 genes were analysed, and we found that they contained multiple disease resistance and hormone elements, such as WRKY71OS, a common disease resistance element that is also involved in the GA signalling pathway and inhibits starch hydrolysis. The comprehensive annotation and expression profiling performed in this study increased our understanding of the TaAP family genes in wheat growth and development, and the results can be used as a basis for further study of candidate TaAP genes involved in powdery mildew resistance mechanisms.

Wheat powdery mildew, which is mainly caused by Blumeria graminis f. sp. tritici (Bgt), seriously damages wheat production. The wheat-Thinopyrum intermedium alien addition disomic line germplasm SN6306, being one of the important sources of genes for wheat resistance, is highly resistant to Bgt E09 and to many other powdery mildew physiological races. However, knowledge on the resistance mechanism of SN6306 remains limited. Our study employed high-throughput RNA sequencing based on next-generation sequencing technology (Illumina) to obtain an overview of the transcriptome characteristics of SN6306 and its parent wheat Yannong 15 (YN15) during Bgt infection. The sequencing generated 104,773 unigenes, 9909 of which showed varied expression levels. Among the 9909 unigenes, 1678 unigenes showed 0 reads in YN15. The expression levels in Bgt-inoculated SN6306 and YN15 of exactly 39 unigenes that showed 0 or considerably low reads in YN15 were validated to identify the genes involved in Bgt resistance. Among the 39 unigenes, 12 unigenes were upregulated in SN6306 by 3-45 times. These unigenes mainly encoded kinase, synthase, proteases, and signal transduction proteins, which may play an important role in the resistance against Bgt. To confirm whether the unigenes that showed 0 reads in YN15 are really unique to SN6306, 8 unigenes were cloned and sequenced. Results showed that the selected unigenes are more similar to SN6306 and Th. intermedium than to the wheat cultivar YN15. The sequencing results further confirmed that the unigenes showing 0 reads in YN15 are unique to SN6306 and are most likely derived from Th. intermedium (Host) Nevski. Thus, the genes from Th. intermedium most probably conferred the resistance of SN6306 to Bgt., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Grain protein content in wheat (Triticum aestivum L.) is generally considered a highly heritable character that is negatively correlated with grain yield and yield-related traits. Quantitative trait loci (QTL) for protein content was mapped using data on protein content and protein content conditioned on the putatively interrelated traits to evaluate possible genetic interrelationships between protein content and yield, as well as yield-related traits. Phenotypic data were evaluated in a recombinant inbred line population with 302 lines derived from a cross between the Chinese cultivar Weimai 8 and Luohan 2. Inclusive composite interval mapping using IciMapping 3.0 was employed for mapping unconditional and conditional QTL with additives. A strong genetic relationship was found between protein content and grain yield, and yield-related traits. Unconditional QTL mapping analysis detected seven additive QTL for protein content, with additive effects ranging in absolute size from 0.1898% to 0.3407% protein content, jointly accounting for 43.45% of the trait variance. Conditional QTL mapping analysis indicated two QTL independent from yield, which can be used in marker-assisted selection for increasing yield without affecting grain protein content. Three additional QTL with minor effects were identified in the conditional mapping. Of the three QTLs, two were identified when protein content was conditioned on yield, which had pleiotropic effects on those two traits. Conditional QTL mapping can be used to dissect the genetic interrelationship between two traits at the individual QTL level for closely correlated traits. Further, conditional QTL mapping can reveal additional QTL with minor effects that are undetectable in unconditional mapping.