Genetic Manipulation for Enhancing Calcium Content in Potato Tuber

Abstract

Increased calcium (Ca) in potatoes may increase the production rate by enhancing tuber quality and storability. Additionally, increased Ca levels in important agricultural crops may help ameliorate the incidence of osteoporosis. However, the capacity to alter Ca levels in potato tubers through genetic manipulations has not been previously addressed. Here we demonstrate that potato tubers expressing the Arabidopsis H+/Ca2+ transporter sCAX1 (N-terminal autoinhibitory domain truncated version of CAtion eXchanger 1) contain up to 3-fold more Ca than wild-type tubers. The increased Ca appears to be distributed throughout the tuber. The sCAX1-expressing potatoes have normally undergone the tuber/plant/tuber cycle for three generations; the trait appeared stable through successive generations. The expression of sCAX1 does not appear to alter potato growth and development. Furthermore, increased Ca levels in sCAX1-expressing tubers do not appear to alter tuber morphology or yield. Given the preponderance of potato consumption worldwide, these transgenic plants may be a means of marginally increasing Ca intake levels in the population. To our knowledge, this study represents the first attempts to use biotechnology to increase the Ca content of potatoes.

Ectopic expression of a maize calreticulin mitigates calcium deficiency-like disorders in sCAX1-expressing tobacco and tomato

“…16 To determine how the co-expression of CRT in sCAX1-expressing tomato alters 17 Ca 2+ concentration in the fruit cells, the total accumulation of Ca 2+ in the tomato fruits 18 of wild-type, sCAX1-, CRT-, and sCAX1+CRT-expressing T2 generation plants was 19 analyzed. All the sCAX1-and sCAX1+CRT-expressing tomatoes showed 20 significantly higher Ca 2+ content than wild-type tomatoes (Fig. 4d).…”

“…Gradients across these organelles are important for 18 normal cellular function and for the regulation of metabolic processes which requires 19 punctilious regulation of cytosolic Ca 2+ . These gradients are established by a 20 dynamic balance between influx and efflux of Ca 2+ across each of the cellular 21 membranes. (Park et al 2005b; Park et al 2009).…”

“…These gradients are established by a 20 dynamic balance between influx and efflux of Ca 2+ across each of the cellular 21 membranes. (Park et al 2005b; Park et al 2009). However, in some cases, these changes also 12 produce deleterious phenotypes that impact yield (Hirschi 1999; Park et al 2005a).…”

“…15 Tobacco lines expressing sCAX1 increase Ca 2+ content in their tissues, but also 16 display severe Ca 2+ deficiency-like symptoms, such as apical leaf tip burning and 17 sensitivity to ion imbalances (Hirschi 1999). In addition, while the fruits of 18 sCAX1-expressing tomato plants accumulate higher total Ca 2+ than vector control 19 plants, the sCAX1-expressing tomatoes show increased incidence of distinct necrotic 20 lesions in the distal portion of fruits, termed blossom-end rot (BER), which is 21 presumed to be caused by aberrant Ca 2+ homeostasis in fruit cells (Park et al 2005a 15 without adversely affecting yield. To our knowledge, this study represents the first 16 attempts to increase the Ca 2+ content of plants using co-expression of two genes 17 which play important roles in the regulation of Ca 2+ .…”

“…The intensity of the signal in sCAX1+CRT-2 and -3 may suggest that sCAX1 and CRT transcripts were expressed only in the sCAX1 and CRT 18 transgenic lines, respectively; while both sCAX1 and CRT transcripts accumulated in 19 the sCAX1+CRT-2, -3, and -13 transgenic lines (Fig 1c). 20 Previous tomato studies demonstrate that sCAX1 expression also causes apical 21 burning and the development of distinct necrotic lesions in the distal portion of fruits 22 11 (BER). Thus, we were interested in determining whether co-expression of CRT in 1 sCAX1-expressing tomato plants would alleviate the symptoms.…”