NBRI - Plant Gene Expression

Plant Gene Expression

Dr. P. Nath Scientist G	Phone no. 91-522-2205831-35 Ext. 956	p.nath@nbri.res.in
Dr. Anirudh P. Sane Scientist E I	Phone no. 91-522-2205831-35 Ext. 958	ap.sane@nbri.res.in
Dr. P. K. Trivedi Scientist E I	Phone no. 91-522-2205831-35 Ext. 958	prabodht@nbri.res.in
Dr. Vidhu A. Sane Scientist C	Phone no. 91-522-2205831-35 Ext. 959	va.sane@nbri.res.in

Group works on

The laboratory of Plant gene Expression is engaged in the development of post harvest biotechnology for fruit, flower and vegetables for sustainable agriculture practices. There has been many fold increase in the production of fruits, vegetables and flowers in the last couple of decades. This could be attributed mainly to good agriculture practices as well as development of high yielding varieties. However, in cases of perishable fruits and vegetables as also exotic cut flowers the value destruction has also increased proportionately due to lack of appropriate post harvest measures. We have initiated recombinant DNA technology program in fruits, vegetable and flowers to develop transgenic varieties, which show desired post harvest behaviour and have higher shelf and vase life. The crops selected are banana, mango, tomato, rose and gladiolus.

Achievements

Molecular biology of ripening in climacteric fruits

Banana and mango are major fruit crops for export and there are certain exotic but delicate varieties, which do not find place in export market as they perish quickly. We at the Plant Gene expression lab. are making efforts to develop such varieties through gene manipulations that have higher shelf life. Genes for cell wall modifying enzymes such as PG, XET, pectate lyase and expansins and genes for ethylene biosynthesis and perception such as ACO, ACS and etr have been cloned and characterized from both banana and mango. Transgenic tomato plants expressing antisense ACO gene from banana show delayed post harvest softening of ripe tomato. Using differential display techniques and PCR select subtractive hybridisation several novel up regulated and down regulated genes in banana have been identified. Many of these genes show fruit specific and ripening related expression. Functional analysis of these genes through over expression and antisense expression is underway in tomato and banana. We have also cloned at least three proximal promoters from the genes specific to ripening in banana. These are being characterized through transient expression analysis of promoter-GUS fusion construct in order to realize if these promoters can be utilized to express desired genes specifically in fruits. Beside these ethylene responsive factors (ERFs) which are believed to finally control activities of target genes during ripening are being studied in tomatoes. Functional analysis of these factors through transgenics may reveal underlying mechanism of ripening in climacteric fruits.

The molecular basis of petal abscission in rose and senescence in gladiolus

The vase life of flowers is of major consideration in the cut flower industry. A short vase life is undesirable and is mainly caused by two ethylene regulated processes viz. abscission and senescence of petals. Our major aim is to understand the molecular mechanism behind these processes and understand role of ethylene in governing these. We have selected two important cut flowers viz. rose and gladiolus, that respond differently to ethylene, in order to study these processes. In rose, exposure to ethylene results in rapid abscission of petals whereas gladiolus undergoes a gradual senescence. Using mRNA differential display we have identified several genes that are differentially expressed during the formation of the abscission zone in petals in rose and during the process of senescence in gladiolus. Homologues of genes that are known to be involved in cell wall hydrolyses and the ethylene signal pathway have also been identified in rose abscission zones using a PCR based approach. The major aim of these studies is also to identify promoters that drive abscission / senescence specific expression and utilize these promoters and genes to delay the onset of these processes by an antisense or similar approach.

Metabolic engineering of tomato plants for biosynthesis of isoflavones

Isoflavones form a group of distinct secondary metabolites produced predominantly in leguminous plants. These compounds have distinct role in plant defence and root nodulation. The isoflavones, genistein and diadzein, which are naturally occurring are presently being studied for their role in human health. The reported health benefits include relief in menopausal symptoms, reduction in osteoporosis, improvement in blood cholesterol levels and lower risk of certain hormone related cancers and coronary heart diseases. Isoflavones are synthesized in plants from flavone, naringenin and liquiritigenin, by the cytochrome P450 enzyme isoflavone synthase (IFS). IFS and Chalcone isomerase (CHI) are entry point enzymes of isoflavone biosynthesis and therefore the key step for engineering isoflavone production into non-leguminous plants. Metabolic engineering for isoflavones in crops that are not capable of synthesizing isoflavones would provide food manufacturers an alternative to legumes (mostly soy) for the use in their health products. Full-length cDNAs of IFS and CHI genes have been cloned from soybean and attempts to introduce these in tomato are underway.

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