Transcriptional responses of maize seedling root to phosphorus starvation.

Maize (Zea mays) is the most widely cultivated crop around the world, however, it is commonly affected by phosphate (Pi) deficiency and the underlying molecular basis of responses mechanism is still unknown. In this study, the transcriptional response of maize roots to Pi starvation at 3 days after the onset of Pi deprivation was assessed. The investigation revealed a total of 283 Pi-responsive genes, of which 199 and 84 genes were found to be either up- or down-regulated respectively, by 2-fold or more. Pi-responsive genes were found to be involved in sugar and nitrogen metabolic pathways, ion transport, signal transduction, transcriptional regulation, and other processes related to growth and development. In addition, the expression patterns of maize inorganic phosphorus transporters, acid phosphatase, phytase, 2-deoxymugineic acid synthase1, POD and MYB transcription factor were validated in 178 roots response to low phosphorus stress. of which, two genes encoding phytase and acid phosphatase were significantly induced by Pi deficiency and may play a pivotal role in the process of absorption and re-utilization of Pi in Maize. These results not only enhance our knowledge about molecular processes associated with Pi deficiency, but also facilitate the identification of key molecular determinants for improving Pi use in maize. Moreover, this work sets a framework to produce Pi-specific maize microarrays to study the changes in global gene expression between Pi-efficient and Pi-inefficient maize genotypes.

Variation and their relationship of NAM-G1 gene and grain protein content in Triticum timopheevii Zhuk.

NAM is an important domestication gene and valuable to enhance grain protein contents (GPCs) of modern wheat cultivars. In the present study, 12 NAM-G1 genes in Triticum timopheevii Zhuk. (AAGG, 2n=4x=28) were cloned. These genes had the same length of 1546 bp including two introns and three exons, and encoded a polypeptide of 407 amino acid residues which contained a N-terminal NAC domain with five sub-domains, and a C-terminal transcriptional activation region (TAR). They were highly similar to the previously published functional NAM-B1 gene DQ871219 from T. turgidum ssp. dicoccoides Körn. (AABB, 2n=4x=28) in both the nucleotide and protein sequences, with a very high identity of 99.5%. The differences among the 12 NAM-G1 genes resulted from 17 SNPs including 14 transitions and 3 transversions. They had outstandingly different expression levels in qRT-PCR. And, their relative expression quantities were significantly positively correlated with GPC of the accessions. In addition, the difference in amino acid sequences of the NAM-G1 genes may also affect the GPC variation.

[Advances in study of plant miRNAs under stressed environmental conditions].

Biotic and abiotic stresses influence plant growth and cause great loss to crop yield. In the long course of evolution, plants have developed intricate biological mechanism to resist stressed conditions. Under various stressed conditions, not only the protein-coding genes, but also the non-protein-coding genes were induced for response. More and more researches showed that the transcripts of these non-protein-coding genes played important role in regulation of gene expression. miRNA is one of the groups in these no-coding regulatory small RNAs. Recent findings showed that in order to resist the biotic and abiotic stresses, expression of microRNA (miRNA) genes will be induced and their transcripts (miRNAs) can regulate gene expression by guiding target mRNA cleavage or translation inhibition. This paper focused on the advances of plant miRNAs research in stressed conditions, especially induced expression of miRNA and target gene regulation and its role on adaptation under stressed conditions. Then, the methods of miRNA researches in stressed environments are discussed.

[Advances of microarray analysis on plant gene expression under environmental stresses].

Different stressed conditions impair plant growth and further, cause great loss of crop yield and even lead to lose production completely. Increasing resistance/tolerance of crops under stressed conditions is a major goal of numerous plant breeders, and many elegant works are focusing on this area to uncover these complicated mechanisms underlying it. However, the traditional strategies including physiological and biochemical methods, as well as studies on a few genes, can not well understand the overall biological mechanism. Microarray analysis opens a door to uncover these cryptic mechanisms, and has the ability of detecting gene transcription and regulation at genomic level in different plant tissues. And works in association with related methods of proteomics and metabolomics. Therefore, it is possible to locate genes in certain key metabolism pathways. Through these procedures, it is also possible to look for critical genes in the pathway and to well understand the molecular mechanism of resistance/tolerance. These results can be as a guidance for increasing the resistance/tolerance of stressed conditions using biotechnology methods in future. This paper mainly focused on and discussed the advances of microarray analysis of stressed conditions-related genes in plants.

[Identification of QTL associated with tassel branch number and total tassel length in maize].

On the basis of 103 SSR linkage map, QTLs associated with tassel branch number (TBN) and total tassel length (TTL) were studied by composite interval mapping with F3 families, which were developed from the cross N87-1 x 9526 and surveyed for phenotype under normal condition (CK) and drought-stress environment (DS). Four QTLs on chromosomes 2, 5, 7, and 10, respectively, were associated with TBN under DS, two of which were not only repeatedly detected on chromosomes 5 and 7 under the CK but also were linked to some QTLs related to drought tolerance that had already been reported in the same mapping population. The two QTLs controlling TTL were identified on chromosomes 2 and 6 under CK, while three QTLs for TTL were detected on chromosomes 2, 4, and 10 under DS. The QTL on chromosome 2 for TTL was consistent under two environments. Most of QTLs for TBN were partial additive while QTLs for TTL were dominant and over-dominant in terms of gene action.

[Initial identification of quantitative trait loci controlling resistance to banded leaf and sheath blight at elongating and heading date in maize].

The genetic linkage map was constructed with 146 SSR markers based on a maize population consisting of 229 F2 individuals from the cross R15 (resistant) x 478 (susceptible), covering 1666cM on a total of ten chromosomes, with an average interval length of 11.4 cM. The disease index from the population of 229 F24 lines were evaluated for BLSB resistance under artificial inoculation at elongating stage and heading date. With the method of composite interval mapping (CIM) described in QTL cartographer v2.0 procedure, 9 QTLs among of 17 QTLs were identified on 1, 2, 3, 4, 5, 6 and 10 chromosomes at Jointing Stage, accounting for 3.72% to 9.26% of the phenotypic variance. The other 10 QTLs were identified on 2, 3, 4, 5, 6, 8 and 9 chromosomes at elongating stage and heading date, accounting for 4.27% to 9.27% of the phenotypic variance. Among of them, two QTLs were detected at two stages, which were located between bnlgl600-umc1818 and umc1006-umc1723 on chromosome 2 and 6, respectively. The result indicated that the significant difference about QTL Controlling Resistance between the two stages had a close connection with Developing Stages, which was showed on the resistance of banded leaf and sheath blight in maize. So this result provided new information to the resistance breeding of maize.