Chapter 23 - Expression of Pea (Pisum sativum) Seed Ferritin Gene in Indian Mustard (Brassica juncea) Enhances Accumulation of Iron and Cadmium

Abstract

Ferritin is a ubiquitous protein that sequesters and stores iron in a bioavailable form. In this study, our goal was to develop transgenic plants with increased iron content and check for the tolerance and accumulation of cadmium by expressing a pea seed ferritin cDNA in Indian mustard (Brassica juncea cv. Pusa Jai Kisan). Transgenic mustard, with high iron content in leaves, has been produced by transferring pea seed ferritin cDNA under the control of a CaMV35S promoter through genetic transformation via Agrobacterium tumefaciens. The expression of ferritin mRNA and protein in leaves of T1 generation transgenic mustard plants was confirmed by reverse transcription polymerase chain reaction and Western blot analysis. Atomic absorption spectroscopy of the leaves of transgenics showed that iron levels were twofold higher than the leaves of wild-type plants. Upregulation of the ferric reductase in transgenics indicates the iron sequestration in transgenics. When observed in atomic absorption spectroscopy and energy dispersive angle X-ray analysis, the percentage increase of iron levels in the seeds was not significantly higher compared with leaves in transgenics, indicating that the iron sequestration was efficient in leaves compared with seeds. Two-week-old wild-type and transgenic mustard seedlings grown in agar medium at varying concentrations of cadmium, iron, and a combination, when evaluated for tolerance and accumulation, showed that transgenics were significantly more tolerant than wild-type plants even at higher concentrations of cadmium (400μM), iron (700μM), and a combination (700 Fe + 200CdμM) with respect to morphology and accumulation of the metals. Iron and cadmium accumulating ability has been studied in Indian mustard upon transfer of the pea seed ferritin.