Presence, mobility and bioactivity of antifungal proteins in sorghum caryopses /
Changes in antifungal proteins (AFP) during sorghum
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739667711&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Changes in antifungal proteins (AFP) during sorghum caryopsis development, maturation and germination were investigated to explore possibilities of utilizing seed AFPs to minimize grain molding. AFP levels among sorghums were correlated with grain mold rating. AFP location within caryopses and changes during imbibition were investigated. Several AFPs were purified, antibodies raised against them, and their bioactivity against grain molding pathogens was tested. Sormatin, chitinase and glucanase levels peaked 30 days after anthesis (DAA) and ribosome-inactivating protein (RIP) levels peaked 21 DAA. AFP levels were significantly influenced by extent of grain molding and weathering. Sormatin, chitinase and glucanase levels increased during seed germination in caryopses and shoots. RIP was hydrolyzed during seed germination and levels of hydrolyzed proteins increased during germination in caryopses and shoots. Sormatin (0-190 ug/g seed) and chitinase (0-20 [ug/g seed) levels were significantly different among sorghums. Sormatin levels at physiological maturity positively correlated with mold rating (R2=0.67), while chitinase levels 15 DAA exhibited a negative correlation (R2=0.40). Sormatin and chitinase were detected predominantly in the peripheral endosperm tissues. Upon imbibition, AFP extractability and levels increased within 2 hr, and migrated from endosperm towards pericarp by 24 hr. AFPs leached out of immature caryopses, but were retained in pericarp of mature caryopses. Further, tannins, present in Type II and III sorghums, bound AFPs rendering them inextractable. Successful bioassays were developed to elicit bioactivity of AFPs. A fraction containing several AFPs was inhibitory against F. moniliforme and C. lunata. F. moniliforme exhibited hyphal rupture at protein levels as low as 20 [ug, while C. lunata required 20- 100 jig of protein. Spore germination of both species was completely inhibited by less than 100 [ug protein. AFPs also completely inhibited spore germination of both A. flavus and A. parasiticus. Aspergillus species did not exhibit hyphal rupture when treated with AFPS. Therefore, these studies have established physiological changes in AFPs during caryopses development, maturation, germination and imbibition; identified parameters with which to evaluate grain mold resistance; proposed a mode of action by which AFPs act upon fungi; and generated hypotheses on the workings of seed AFPs to mitigate other seed borne diseases. |
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| Item Description: | Vita. "Major Subject: Food Science and Technology". |
| Physical Description: | xiii, 121 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 95-115. |