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The molecular mechanism for sensing and transducing the stress signals initiated by K deprivation in plants remains unknown. Here, we found that the expression of AtHELPS, an Arabidopsis DExD/H box RNA helicase gene, was induced by low-K, zeatin and cold treatments, and downregulated by high-K stress. To further investigate the expression pattern of AtHELPS, pAtHELPS::GUS transgenic plants were generated. Histochemical staining indicated that AtHELPS is mainly expressed in the young seedlings and vascular tissues of leaves and roots. Using both helps mutants and overexpression lines, we observed that, in the low-K condition, AtHELPS affected Arabidopsis seed germination and plant weight. Interestingly, the mRNA levels of AKT1, CBL1/9 and CIPK23 in the helps mutants were much higher than in the overexpression lines under low-K stress. Moreover, under low-K stress, the helps mutants displayed increased K influx, whereas the overexpression line of AtHELPS had a lower flux rate in the roots by the noninvasive micro-test technique. Taken together, these results provide information for the functional analysis of plant DEVH box RNA helicases, and suggest that AtHELPS, as an important negative regulator, plays a role in K deprivation stress. The Arabidopsis DExD/H box RNA helicase gene, AtHELPS, was mainly expressed in young seedlings and vascular tissues of leaves and roots. It was also induced by low potassium stress and down-regulated by high potassium stress. In the low potassium condition AtHELPS affected Arabidopsis seed germination and plant weight by affecting transcription of AKT1, CBL1/9 and CIPK23 and K influx rate [ABSTRACT FROM AUTHOR]

Mitogen-activated protein kinase (MAPK) cascades play important roles in mediating pathogen responses and reactive oxygen species signaling. In plants, MAPKs are classified into four major groups (A-D). Previous studies have mainly focused on groups A and B, but little is known about group C. In this study, we functionally characterized a stress-responsive group C MAPK gene ( GhMPK2) from cotton. Northern blot analysis indicated that GhMPK2 was induced not only by signaling molecules, such as ethylene and methyl jasmonate, but also by methyl viologen-mediated oxidative stress. Transgenic tobacco ( Nicotiana tabacum) plants that overexpress GhMPK2 displayed enhanced resistance to fungal and viral pathogens, and the expression of the pathogenesis-related (PR) genes, including PR1, PR2, PR4, and PR5, was significantly increased. Interestingly, the transcription of 1-aminocyclopropane-1-carboxylic acid synthase ( ACS) and 1-aminocyclopropane-1-carboxylic acid oxidase ( ACO) was significantly upregulated in transgenic plants, suggesting that GhMPK2 positively regulates ethylene synthesis. Moreover, overexpression of GhMPK2 elevated the expression of several antioxidant enzymes, conferring on transgenic plants enhanced reactive oxygen species scavenging capability and oxidative stress tolerance. These results increased our understanding of the role of the group C GhMPK2 gene in multiple defense-signaling pathways, including those that are involved in responses to pathogen infection and oxidative stress. In this study, functional characterization of a cotton group C mitogen-activated protein kinase (MAPK) gene ( GhMPK2) was carried out. The expression of GhMPK2 was induced by signaling molecules and oxidative stress. Overexpression of GhMPK2 significantly elevated the expression of the pathogenesis-related ( PR), signaling-related and antioxidative genes, and thereby enhanced the transgenic plants disease resistance and oxidative stress tolerance. [ABSTRACT FROM AUTHOR]

Currently, the molecular regulation mechanisms involved in the early development of maize brace root are poorly known. To gain insight into the transcriptome dynamics that are associated with its development, genome-wide gene expression profiling was conducted by Solexa sequencing (Illumina Inc., San Diego, CA, USA). More than five million tags were generated from the stem node tissues without and with just-emerged brace roots, including 149 524 and 178 131 clean tags in the two libraries, respectively. Of these, 82 864 (55.4%) and 91 678 (51.5%) tags were matched to the reference genes. The most differentially expressed tags with a log ratio > 2 or < −2 ( P < 0.001) were analyzed further, representing 143 up-regulated and 152 down-regulated genes, except for unknown transcripts, which were classified into 11 functional categories. The most enriched categories were those of metabolism, signal transduction and cellular transport. Many genes or biological pathways were found to be commonly shared between brace root and lateral or adventitious root development, such as genes participating in cell wall degradation and synthesis, auxin transport and signaling, ethylene signaling, etc. Next, the expression patterns of 20 genes were assessed by quantitative real-time PCR, and the results obtained showed general agreement with the Solexa analysis. Furthermore, a comparison of the brace root transcriptome with that of maize primary root revealed substantial differences in the categories and abundances of expressed transcripts. In conclusion, we first reveal the complex changes in the transcriptome during the early development of maize brace root and provide a comprehensive set of data that are essential for understanding its molecular regulation. [ABSTRACT FROM AUTHOR]