Physiological and Biochemical Features of Embryogenic and Non-embryogenic Peach Palm (Bactris gasipaes Kunth) Cultures

Maria Carolina Andrade Nascimento-Gavioli

Maria Carolina Andrade Nascimento-Gavioli

Joseph Francis Ree

Joseph Francis Ree

Neusa Steiner

Neusa Steiner

Miguel Pedro Guerra

Miguel Pedro Guerra

Plant somatic cells are highly plastic under the adequate culturing conditions; they can change their epigenetic, genetic, biochemical, and hormonal profiles to undergo dedifferentiation into an embryogenic state. These embryogenic cells can be induced to reenter the cell cycle and develop into somatic embryos, which can then be germinated, rooted, acclimated, and transferred to the field like any plant from a zygotic embryo. However, multiple types of tissue can be cultivated in vitro under the exact same culture conditions, and, indeed, from the exact same explant. We wanted to understand more about why cells might take different paths at some developmental crossroads. To that end, we selected a range of biochemicals involved in many cellular processes for analysis: the plant hormones indole-3-acetic acid and abscisic acid; polyamines; amino acids; and total phenolics. Then, we collected samples of embryogenic cultures displaying proembryogenic callus and developing globular embryos and fibrous non-embryogenic callus, extracted the molecules of interest, and measured them. Our results showed significant differences between either culture type. Embryogenic callus contained higher concentration of either plant hormone and total amino acids, whereas the nonembryogenic culture contained higher total polyamines and phenolics. This might suggest that the early cell differentiation might have included a genetic ‘switch’ that caused a large change to cellular metabolism that led to the development of two radically different types of tissue under the exact same culture conditions. Tracing this change back to its branching point early in culture induction might reveal not only more about the biology of embryogenesis, but other, less studied, mechanisms involved in determining plant cell fate.

Maria Carolina Andrade Nascimento-Gavioli, Gabriela Claudia Cangahuala-Inocente, Douglas Steinmacher, Joseph Francis Ree, Neusa Steiner, Miguel Pedro Guerra.  Physiological and Biochemical Features of Embryogenic and Non-embryogenic Peach Palm (Bactris gasipaes Kunth) Cultures.  In Vitro Cellular & Developmental Biology-Plant, 53:33-40, 2017.


Enhancement of sheath blight tolerance in transgenic rice by combined expression of tobacco osmotin (ap24) and rice chitinase (chi11) genes

Left: Prof. K. Veluthambi. Right clockwise from top, Dr. Selvi, Dr. G. Sridevi, Dr. Nagrani Mahajan, Dr. R. Sripriya, Dr. C. Parameswari, Dr. Lakshmikumari and Dr. Jasmine Shah

Sheath blight disease (SBD) caused by the fungus Rhizoctonia solani is a major constraint in rice cultivation.  Routinely, yield loss due to SBD is in the range of 10-30% but can increase even up to 50% when there is a severe disease outbreak.  Due to lack of stable disease resistance germplasm, breeding for SBD resistance in rice has not been successful.  Although chemical control methods using fungicides yield limited effectiveness, the undesirable effects of these chemicals on human health and environment are major concerns.  Naturally, plants defend themselves against fungal pathogens by producing a repertoire of pathogen-related (PR) proteins that act in a synergistic manner to control the fungal growth.  In many experiments reported in the past, genetic engineering to over express individual PR-protein genes yielded limited success in reducing fungal disease symptoms.

In the present study, we demonstrate that, over expression of a combination of two PR-protein genes with different modes of action can synergistically control SBD in rice.  Combined expression of the rice chitinase gene (chi11, PR-3) which degrades the fungal cell wall and tobacco osmotin gene (ap24, PR-5) which alters membrane permeability caused a more pronounced reduction of SBD in rice, than obtained with either of the PR-protein genes.  This report shows that expression of combination of PR-protein genes in transgenic plants is a powerful strategy to control fungal diseases in crops.

Rajasekaran Sripriya, Chidambaram Parameswari, Karuppannan Veluthambi. Enhancement of sheath blight tolerance in transgenic rice by combined expression of tobacco osmotin (ap24) and rice chitinase (chi11) genesIn Vitro Cellular & Developmental Biology-Plant, 53:12-21, 2017.