A novel sunshine duration-based photothermal time model interprets the photosensitivity of flower maturity of pecan cultivars.

Although it is well-known and established that light plays important roles in plant development, up to now, there is no substantial improvements in how to deal with the light factor of spring phenology under natural condition. By monitoring the local meteorologic data and mature dates of two types (male and female) of flower from four pecan cultivars during 9 years, it was found that the complementary pattern of growing degree day and sunshine duration helped to maintain a threshold of driving force related to the maturity of pecan flower during 9 years. A novel photothermal time model based on the linear combination of growing degree day and sunshine duration was then proposed and validated to interpret the variance of mature dates of pecan cultivars. Comparative analysis showed that the new model had made extremely significant improvements to the traditional thermal time model. In addition, this model introduced the conversion coefficient K, which quantified the effect of light on the flowering drive, and revealed the differences of base temperature among cultivars. This was the first time that sunshine duration instead of photoperiod was adopted to develop into a verified model on spring phenological event of tree species. It will help to model the spring phenologies of other tree species more reasonably.

Isolation and functional characteristics of the fungus Hypoxylon spp. Sj18 with biocontrol potential.

A fungus with biocontrol potential was isolated from the roots of hickory trees. The strain named sj18 was classified as a member of the genus Hypoxylon (Hypoxylaceae) after multigene phylogenetic analysis (beta-tubulin gene, internal transcribed spacer, 28S large subunit ribosomal RNA gene, and RNA polymerase II subunit gene). The strain grew well on a PDA with an optimum temperature range between 32 and 34 °C. The fungus had obvious inhibitory effects on Botryosphaeria dothidea, Colletotrichum gloeosporioides, and Gibberella moniliformis in fumigation experiments on solid agar plates. In an inoculation experiment of Chinese cabbage, the fungus was also found to have an obvious repellent effect on cabbage caterpillars. In vitro experiments on Petri dishes showed that the fermentation broth of the sj18 strain could kill 100% of Bursaphelenchus xylophilus within 8 h even if the fermentation broth was diluted 8 times. The inoculation test of Arabidopsis thaliana showed that the fungus could promote the lateral root formation of plants and significantly increase their aboveground biomass. Through the analysis of solid phase microextraction (SPME), it was found that the main volatile components of the fermentation products were azulene 65.39% (61.77% + 3.62%), caryophyllene 7.41%, and eucalyptol 6.83% according to the peak area ratio. Therefore, sj18 can be used as a candidate for the further research and development of biocontrol agents.

Identification and characterization of two bamboo (Phyllostachys praecox) AP1/SQUA-like MADS-box genes during floral transition.

Bamboo (Bambusoideae) is by far the largest member of the grass family Poaceae, which is vital to the economy of many countries in the tropics and subtropics. However, the mechanism of flowering of bamboo (Phyllostachys praecox) is still unknown. In this study, we isolated two novel genes from P. praecox and evaluated their functional characteristics. The sequence and phylogenetic analysis indicated that these two genes, named PpMADS1 and PpMADS2, belong to FUL3 and FUL1 clade of Poaceae AP1/SQUA-like genes, respectively. The PpMADS2 possesses a truncated C terminus lacking the highly conserved paleoAP1 motif. It was further confirmed that the truncated C-terminal region was produced by natural sequence deletion in exons, but not by alternative splicing. Ectopic expression of PpMADS1 and PpMADS2 significantly promoted early flowering through upregulation of AP1 in Arabidopsis. Yeast two-hybrid experiments demonstrated that AP1 protein can interact with PpMADS1 but not PpMADS2, suggesting that these two genes may act differently in signaling early flowering of bamboo plants. RT-qPCR and in situ hybridization analysis revealed distinct expression patterns of these two genes in vegetative and reproductive tissues of bamboo. Taken together, our results suggest that both PpMADS1 and PpMADS2 are involved in floral transition, and PpMADS2 might play more important roles than PpMADS1 in floral development of Phyllostachys praecox.

New available SCAR markers: potentially useful in distinguishing a commercial strain of the superior type from other strains of Lentinula edodes in China.

At present, more than 100 strains of Lentinula edodes are cultivated on a commercial scale in China. A simple, reliable, and effective method to distinguish some commercial strains of the superior type from other commercial strains is very important for the Lentinula industry. In this study, 23 commercial strains of L. edodes cultivated widely in China at present were collected and analyzed with randomly amplified polymorphic DNA (RAPD) technique. Three informative dominant sequence characterized amplified region (SCAR) markers were developed by designing three pairs of specific SCAR primers from three sequenced differential RAPD bands, respectively. Based on the three SCAR markers, three different multiplex polymerase chain reaction (PCR) phenotypes were detected among the 23 studied commercial strains and in which a multilocus phenotype characterizing a commercial strain Cr02 of the superior type could potentially be used to distinguish this strain from the other 22 studied commercial strains. To our knowledge, this study is the first to describe the development of a multiplex PCR technique based on SCAR markers for detecting the molecular phenotypes among commercial strains of L. edodes in China.

Molecular cloning, expression analyses and primary evolution studies of REV- and TB1-like genes in bamboo.

Most cultured bamboos are perennial woody evergreens that reproduce from rhizomes. It is unclear why some rhizome buds develop into aerial bamboo shoots instead of new rhizomes. REVOLUTA (REV)-like Class III homeodomain leucine-zipper (HD-Zip) proteins and TEOSINTE BRANCHED1 (TB1)-like transcription factors have been shown to play regulatory roles in meristem initiation and outgrowth. We cloned and analyzed the bamboo (Phyllostachys praecox C.D. Chu & C.S. Chao.) REV- (PpHB1) and TB1-like (PpTB1) gene. Gene expression was mainly detected by in situ hybridization. PpHB1 expression was detected in the tips of lateral buds, on the adaxial portion of the leaf and within the developing procambium, indicating its close correlation to rhizome bud formation and procambial development. PpTB1 expression was mainly detected on the top of buds at later developmental stages, suggesting it was more likely involved in bud outgrowth. Meristem genes might therefore serve as specific molecular markers of rhizome bud development and could be useful in studies designed to elucidate the mechanisms underlying bamboo shoot development. In addition, meristem genes such as TB1-like sequences may be useful in phylogenetic analyses of bamboo species.

Programmed cell death-involved aluminum toxicity in yeast alleviated by antiapoptotic members with decreased calcium signals.

The molecular mechanisms of aluminum (Al) toxicity and tolerance in plants have been the focus of ongoing research in the area of stress phytophysiology. Recent studies have described Al-induced apoptosis-like cell death in plant and animal cells. In this study, we show that yeast (Saccharomyces cerevisiae) exposed to low effective concentrations of Al for short times undergoes enhanced cell division in a manner that is dose and cell density dependent. At higher concentrations of Al or longer exposure times, Al induces cell death and growth inhibition. Several apoptotic features appear during Al treatment, including cell shrinkage, vacuolation, chromatin marginalization, nuclear fragmentation, DNA degradation, and DNA strand breaks, as well as concomitant cell aggregation. Yeast strains expressing Ced-9, Bcl-2, and PpBI-1 (a plant Bax inhibitor-1 isolated from Phyllostachys praecox), respectively, display more resistance to Al toxicity compared with control cells. Data from flow cytometric studies show these three antiapoptotic members do not affect reactive oxygen species levels, but decrease calcium ion (Ca(2+)) signals in response to Al stress, although both intracellular reactive oxygen species and Ca(2+) levels were increased. The data presented suggest that manipulation of the negative regulation process of programmed cell death may provide a novel mechanism for conferring Al tolerance.