Department of Biological Sciences

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Subject: search.filters.subject.Oryza sativa

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    Inhibition of mitochondrial electron transport is the prime cause behind proline accumulation during mineral deficiency in Oryza sativa
    (Springer, 1993) Bhagavatula, Vani
    The concentration of proline in shoots of rice (Oryza sativa) seedlings raised in distilled water was about 3.3 times higher than in the seedlings raised in modified B5 medium. The shoots of seedlings raised in B5 medium which was depleted of calcium, iron, magnesium or potassium had a higher concentration of proline than those grown in standard B5 medium. The shoots of seedlings raised in distilled water with iron had a lower level of proline than those in distilled water. These results suggest that iron deficiency leads to high proline accumulation.
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    Effect of short-term heat treatment of rice seedlings on sensitivity of thylakoid membranes to photoinhibition
    (Springer, 1996) Bhagavatula, Vani
    The after-effects of 24 h high temperature (35 or 45 ~ treatment on the photochemical activities and photooxidative lipid peroxidation, subsequent to their irradiation were studied in 7-d-old etiolated rice (Oryza sativa) seedlings. Photosystem (PS) 1 and PS 2 mediated photoreactions of thylakoids isolated from the seedlings exposed to high temperature did not differ significantly from the thylakoids isolated from control seedlings (25 ~ Hence, all kinds of tested thylakoids were equally efficient in capturing and utilizing radiant energy. The high irradiance induced loss in PS 2 activity and lipid peroxidation measured in terms of malondialdehyde production was more rapid in thylakoids isolated from stressed seedlings as compared to that of control seedlings. Thus the thylakoids isolated from the stressed seedlings were more prone to photodamage than those from the control seedlings.
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    Ectopic expression of rice Xa21 overcomes developmentally controlled resistance to Xanthomonas oryzae pv. oryzae
    (Elsiever, 2010-11-01) Sharma, Rita
    Recognition of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs) activates the innate immune response. The rice PRR, XA21, confers robust resistance at adult stages to most strains of the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo). Seedlings are still easily infected by Xoo, causing severe yield losses. Here we report that Xa21 is induced by Xoo infection and that ectopic expression of Xa21 confers resistance at three leaf stage (three-week old), overcoming the developmental limitation of XA21-mediated resistance. Ectopic expression of Xa21 also up-regulates a larger set of defence-related genes as compared to Xa21 driven by the native promoter. These results indicate that altered regulation of Xa21 expression is useful for developing enhanced resistance to Xoo at multiple developmental stages.
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    Functional delineation of rice MADS29 reveals its role in embryo and endosperm development by affecting hormone homeostasis
    (OUP, 2013) Sharma, Rita
    Rice MADS29 has recently been reported to cause programmed cell death of maternal tissues, the nucellus, and the nucellar projection during early stages of seed development. However, analyses involving OsMADS29 protein expression domains and characterization of OsMADS29 gain-of-function and knockdown phenotypes revealed novel aspects of its function in maintaining hormone homeostasis, which may have a role in the development of embryo and plastid differentiation and starch filling in endosperm cells. The MADS29 transcripts accumulated to high levels soon after fertilization; however, protein accumulation was found to be delayed by at least 4 days. Immunolocalization studies revealed that the protein accumulated initially in the dorsal-vascular trace and the outer layers of endosperm, and subsequently in the embryo and aleurone and subaleurone layers of the endosperm. Ectopic expression of MADS29 resulted in a severely dwarfed phenotype, exhibiting elevated levels of cytokinin, thereby suggesting that cytokinin biosynthesis pathway could be one of the major targets of OsMADS29. Overexpression of OsMADS29 in heterologous BY2 cells was found to mimic the effects of exogenous application of cytokinins that causes differentiation of proplastids to starch-containing amyloplasts and activation of genes involved in the starch biosynthesis pathway. Suppression of MADS29 expression by RNAi severely affected seed set. The surviving seeds were smaller in size, with developmental abnormalities in the embryo and reduced size of endosperm cells, which also contained loosely packed starch granules. Microarray analysis of overexpression and knockdown lines exhibited altered expression of genes involved in plastid biogenesis, starch biosynthesis, cytokinin signalling and biosynthesis.