Zhu Youyong

The Temporal-Spatial Distribution of Light Intensity in Maize and Soybean Intercropping Systems

Abstract: Intercropping can improve field microclimates, decrease the incidence of crop diseases, and increase crop yields, but the reasons for this remain unknown. Solar radiation is the most important environmental influence. To understand the mechanisms of intercropping we established an experiment consisting of three cropping patterns: a monocropping control (treatment A) and two intercropping treatments (B: two rows of maize and two rows of soybean intercropping; C: two rows of maize and four rows of soybean intercropping). Results show that compared to monocropping, intercropping increased the amount of light penetrating to inferior leaves in maize plants. Light intensity reaching maize plants at the heading stage in intercropping increased over two-fold at 30 cm above ground and 10-fold at 70 cm above ground, compared with monocropping. At the flowering to maturity stage, light intensity at 110. 160 and 210 cm above ground among maize plants was greatly increased in intercropping compared with monocropping, by some five-fold, two-fold and 12%, respectively. Moreover, light intensity declined more slowly at the measured heights in the intercropping system compared with monocropping. From the 7–18th leaf, light intensity per leaf increased two-fold in intercropping compared with monocropping. Daily light duration increased more than a mean of 5 h per day per leaf in intercropping compared with monocropping. The biological characters of maize including thousand kernel weight, yield per plant and area of ear leaves were all greater in intercropping than monocropping. These results suggest that, for maize, intercropping improves light density and duration significantly and this may contribute to biomass and yield increases.

Analysis of Secretary Proteins in the Genome of the Plant Pathogenic Fungus Botrytis Cinerea

The signal peptides prediction algorithm SignalP v3.0, subcellular protein location prediction algorithm TargetP.v1.1, potential GPI-anchor sites prediction algorithm big-PI predictor, trans-membrane domains prediction algorithm TMHMM v2.0 and bioinformatics algorithm MEME were used to analyze 16446 protein sequences of Botrytis cinerea. The results showed that there were 579 deduced secretary proteins. Among these proteins, the minimum and maximum of open read frame were 102 bp and 4848 bps respectively and mean score was 1271 bps. The signal peptides’ length was concentrated to 16~39 amino acids and the average length was 21. 122 of these proteins contain the highly conserved host-targeting-motif RxLx within 100 residues adjacent to the signal peptide cleavage site. According to PEDNAT and COG of GenBank database, this motif’s functions include metabolism modification and cell secretion etc. We blast those putative secretary proteins with RxLx motif in GenBenk and found 47.54% of them have highly conserved homologues in other species, among them 74.1% have putative protein domains. This means these proteins may be more stable or earlier origin. We suppose these proteins are candidate participating in the pathogenesis of Botrytis cinerea but we still need more experimental evidence to confirm their definite functions.The signal peptides prediction algorithm SignalP v3.0, subcellular protein location prediction algorithm TargetP.v1.1, potential GPI-anchor sites prediction algorithm big-PI predictor, trans-membrane domains prediction algorithm TMHMM v2.0 and bioinformatics algorithm MEME were used to analyze 16446 protein sequences ofBotrytis cinerea. The results showed that there were 579 deduced secretary proteins. Among these proteins, the minimum and maximum of open read frame were 102 bp and 4848 bps respectively and mean score was 1271 bps. The signal peptides’ length was concentrated to 16~39 amino acids and the average length was 21. 122 of these proteins contain the highly conserved host-targeting-motif RxLx within 100 residues adjacent to the signal peptide cleavage site. According to PEDNAT and COG of GenBank database, this motif’s functions include metabolism modification and cell secretion etc. We blast those putative secretary proteins with RxLx motif in GenBenk and found 47.54% of them have highly conserved homologues in other species, among them 74.1% have putative protein domains. This means these proteins may be more stable or earlier origin. We suppose these proteins are candidate participating in the pathogenesis of Botrytis cinerea but we still need more experimental evidence to confirm their definite functions.

Chlorimuronethyl Resistance Selectable Marker Unsuited for the Transformation of Rice Blast Fungus (Magnaporthe Grisea)

Chlorimuronethyl resistance gene is increasingly used as a selectable marker for transformation, especially fungal transformation. Magnaporthe grisea is an important model organism for investigating fungal pathogenicity, and Agrobacterium tumefaciens-mediated transformation (ATMT) is used for functional mutagenesis of the fungus. However, our results showed that rice blast strains collected from infectious rice fields have highly conserved resistance to chlorimuronethyl, even comparable to transformants which carrying chlorimuronethyl resistance genes as selectable marker in laboratory conditions. PCR results showed that all tested field strains presented the amplified products of the same size as the selectable marker amplified from plasmid carrying chlorimuronethyl gene. Sequence analysis of PCR products amplified from field strains confirmed that field strains harbored the highly identity homolog of chlorimuronethyl resistance gene. Blast search in GenBank suggested that the fragment is presenting in reference genome sequence of 70-15, but it is not a wide-spread gene in other organisms, excepted for Herpetosiphon aurantiacus. Although the origin and reason of the conserved chlorimuronethyl resistance gene in field isolates of blast fungus is unclear, the ecological function of the gene is noteworthy.Chlorimuronethyl resistance gene is increasingly used as a selectable marker for transformation, especially fungal transformation. Magnaporthe grisea is an important model organism for investigating fungal pathogenicity, and Agrobacterium tumefaciens-mediated transformation (ATMT) is used for functional mutagenesis of the fungus. However, our results showed that rice blast strains collected from infectious rice fields have highly conserved resistance to chlorimuronethyl, even comparable to transformants which carrying chlorimuronethyl resistance genes as selectable marker in laboratory conditions. PCR results showed that all tested field strains presented the amplified products of the same size as the selectable marker amplified from plasmid carrying chlorimuronethyl gene. Sequence analysis of PCR products amplified from field strains confirmed that field strains harbored the highly identity homolog of chlorimuronethyl resistance gene. Blast search in GenBank suggested that the fragment is presenting in reference genome sequence of 70-15, but it is not a wide-spread gene in other organisms, excepted for Herpetosiphon aurantiacus. Although the origin and reason of the conserved chlorimuronethyl resistance gene in field isolates of blast fungus is unclear, the ecological function of the gene is noteworthy.

Recognition and Analysis of a Host-Targeting Motif in the Genome of Fungus Magnaporthe Grisea

A highly conservative host-targeting motif composed of 4 amino acid residues, namely, RxLx was reported to be present only in virulence proteins of malarial parasites (Plasmodium species) and the oomycete avirulence(Avr) protein of Phytophthora. In the present study, we analyzed the secretory proteins of the rice blast fungus Magnaporthe grisea that were predicted by bioinformatics and comparative genomic tools to determine whether the RxLx motif is present in the secretory proteins. In 297 of 1270 secretory proteins, the RxLx motif was detected within a region of 100 amino acids downstream the N-terminal signal peptide cleavage sites. A comparison with the PEDANT database revealed that RxLx motif-containing proteins included enzymes for the degradation of plant cell wall components such as cellulose, endoxylanase, endoglucanase and cutinase hydrolase for degradation of plant cell membrane and cellular contents, this suggests that the RxLx motif-containing proteins probably functioned as virulence proteins and were primarily involved in interaction between the rice blast fungus and host cells. So, our results support the idea that the host -targeting motif (HTM) is a conserved transport machinery, which imply that divergent eukaryotic pathogens might share common mechanisms of pathogenicity. This research will provide useful materials to elucidate whether similar or distinct pathogenic secretion signlals in different eukaryotic pathogens and can be helpful to validate predicted function of the HTM in vivo.