Apurba Anirban

Recently, a novel purple-pericarp super-sweetcorn line, ‘Tim1’ (A1A1.sh2sh2) was derived from the purple-pericarp maize ‘Costa Rica’ (A1Sh2.A1Sh2) and white shrunken2 (sh2) super-sweetcorn ‘Tims-white’ (a1sh2.a1sh2), however, information regarding anthocyanin biosynthesis genes controlling purple colour and sweetness gene is lacking. Specific sequence differences in the CDS (coding DNA sequence) and promoter regions of the anthocyanin biosynthesis structural genes, anthocyanin1 (A1), purple aleurone1 (Pr1) and regulatory genes, purple plant1 (Pl1), plant colour1 (B1), coloured1 (R1), and the sweetcorn structural gene, shrunken2 (sh2) were investigated using the publicly available annotated yellow starchy maize, B73 (NAM5.0) as a reference genome. In the CDS region, the A1, Pl1 and R1 gene sequence differences of ‘Tim1’ and ‘Costa Rica’ were similar, as they control purple-pericarp pigmentation. However, the B1 gene showed similarity between the ‘Tim1’ and ‘Tims-white’ lines, which may indicate that it does not have a role in controlling pericarp colour, unlike the report of a previous study. In the case of the Pr1 gene, in contrast to ‘Costa Rica’, 6- and 8-bp dinucleotide (TA) repeats were observed in the promoter region of the ‘Tims-white’ and ‘Tim1’ lines, respectively, indicating the defective functionality (redder colour in ‘Tim1’ rather than purple in ‘Costa Rica’) of the recessive pr1 allele. In sweetcorn, the structural gene (sh2), sequence showed similarity between purple-sweet ‘Tim1’ and its white-sweet parent ‘Tims-white’, as both display a shrunken phenotype in their mature kernels. These findings revealed that the developed purple-sweet line is different to the reference yellow-nonsweet line in both the anthocyanin biosynthesis and sweetcorn genes.

Purple-pericarp sweetcorn accessions, derived from crossing purple-pericarp maize with white shrunken2 sweetcorn, were assessed for differences in anthocyanin profile at both sweetcorn eating stage and at full kernel maturity. The ‘Tim1’ sweetcorn line developed a similar total anthocyanin concentration to its ‘Costa Rica’ parent when assessed at sweetcorn-eating stage. At full maturity it surpassed the purple maize parent, but this was mainly due to the presence of starch diluting the anthocyanin concentration of the latter. The anthocyanin/colour relationship was affected by both total anthocyanin concentration and the ratio of cyanidin- to pelargonidin-based anthocyanins. Malonylation of anthocyanins was also found to vary and did not appear to be linked with either cyanidin:pelargonidin ratio or total anthocyanin concentration. In addition, anthocyanin synthesis was affected by kernel maturity at harvest, with colour development increasing in conjunction with a progression of anthocyanin development across the kernel surface. Pigmentation was present in the aleurone, pericarp and vitreous endosperm of kernels of the purple-pericarp maize parent and purple-pericarp sweetcorn accessions when fully mature, but pigmentation was only apparent in the pericarp at sweetcorn-eating stage. Importantly for consumers, anthocyanin pigmentation covered almost the entire kernel surface at sweetcorn-eating stage.

The existence of purple-pericarp super-sweetcorn based on the supersweet mutation, shrunken2 (sh2), has not been previously reported, due to its extremely tight genetic linkage to a non-functional anthocyanin biosynthesis gene, anthocyaninless1 (a1). Generally, pericarp-pigmented starchy purple corn contains significantly higher anthocyanin. The development of purple-pericarp super-sweetcorn is dependent on breaking the a1–sh2 tight genetic linkage, which occurs at a very low frequency of < 1 in 1000 meiotic crossovers. Here, to develop purple-pericarp super-sweetcorn, an initial cross between a male purple-pericarp maize, ‘Costa Rica’ (A1Sh2.A1Sh2) and a female white shrunken2 super-sweetcorn, ‘Tims-white’ (a1sh2.a1sh2), was conducted. Subsequent self-pollination based on purple-pericarp-shrunken kernels identified a small frequency (0.08%) of initial heterozygous F3 segregants (A1a1.sh2sh2) producing a fully sh2 cob with a purple-pericarp phenotype, enabled by breaking the close genetic linkage between the a1 and sh2 genes. Resulting rounds of self-pollination generated a F6 homozygous purple-pericarp super-sweetcorn (A1A1.sh2sh2) line, ‘Tim1’. Genome sequencing revealed a recombination break between the a1 and yz1 genes of the a1–yz1-x1–sh2 multigenic interval. The novel purple-pericarp super-sweetcorn produced a similar concentration of anthocyanin and sugar as in its purple-pericarp maize and white super-sweetcorn parents, respectively, potentially adding a broader range of health benefits than currently exists with standard yellow/white sweetcorn.

Recently, a novel purple-pericarp super-sweetcorn line, ‘Tim1’ ( A1A1 . sh2sh2 ) is derived from the purple-pericarp maize ‘Costa Rica’ ( A1Sh2 . A1Sh2 ) and white shrunken2 ( sh2 ) super-sweetcorn ‘Tims-white’ ( a1sh2 . a1sh2 ), however information regarding purple colour controlling anthocyanin biosynthesis genes and sweetcorn gene is lacking. Specific sequence differences in the CDS (coding DNA sequence) and promoter regions of the anthocyanin biosynthesis structural genes, anthocyanin1 ( A1 ), purple aleurone1 ( Pr1 ) and regulatory genes, purple plant1 ( Pl1 ), plant colour1 ( B1 ), coloured1 ( R1 ), and the sweetcorn structural gene, shrunken2 ( sh2 ) were investigated using the publicly available annotated yellow starchy maize, B73 (NAM5.0) as a reference genome. In the CDS region, the A1, Pl1 and R1 gene sequence differences of ‘Tim1’ and ‘Costa Rica’ were similar, as they control purple-pericarp pigmentation, however the B1 gene showed similarity between the ‘Tim1’ and ‘Tims-white’ lines, which may indicate that it does not have a role in controlling pericarp colour, unlike a previous study. In case of Pr1 gene, unlike ‘Costa Rica’, 6- and 8-bp dinucleotide (TA) repeats were observed in the promoter region of the ‘Tims-white’ and ‘Tim1’ lines, respectively, indicating the defective functionality (redder colour in ‘Tim1’ than purple in ‘Costa Rica’) of the recessive pr1 allele. In the sweetcorn structural gene ( sh2 ), sequence similarity was observed between purple-sweet ‘Tim1’ and its white-sweet parent ‘Tims-white’, as both display a shrunken phenotype in their mature kernels. These findings revealed that the developed purple-sweet line is different than the reference yellow-nonsweet line regarding both the anthocyanin biosynthesis and sweetcorn genes.

Anthocyanins, secondary metabolites of pigmented corns consisting of cyanidin-, pelargonidin- and peonidin-based glucoside. While cyanidin-peonidin types are responsible for purple-pigmentation, pelargonidin type is responsible for red-pigmentation. This study examined anthocyanin concentrations in a novel purple-pericarp shrunken2 sweetcorn ‘Tim’ lines in comparison to the parental purple-pericarp ‘Costa Rica’ maize’ and white sweetcorn ‘Tims-white’ lines. The study found similar concentrations of anthocyanin in both ‘Tim1’ and the ‘Costa Rica’, at sweetcorn eating stage, whereas ‘Tims-white’ has no detectable anthocyanin. Total anthocyanins found in the ‘Costa Rica’ and ‘Tim1’, ‘Tim2’, ‘Tim4’ and ‘Tim5’ lines were 255.79, 253.03, 238.10, 198.66, and 221.36 mg/100 g FW (fresh weight), respectively. In all the developed purple-sweetcorn ‘Tim’ lines along with the purple maize parent, the cyanidin-peonidin (purple) proportion of total anthocyanin was 78-93%, as the predominant anthocyanin pigment. The anthocyanin concentration in ‘Tim1’ at eating stage was significantly much higher than currently exists with other coloured fruits.

The existence of purple-pericarp super-sweetcorn based on the most common supersweet mutation, shrunken2 ( sh2 ), has not been previously reported, partly due to its extremely tight genetic linkage to a non-functional anthocyanin biosynthesis gene, anthocyaninless1 ( a1 ). Generally, both aleurone- and pericarp-pigmented purple corn is starchy, the latter of which contains significantly higher anthocyanin compared to the former. The development of purple-pericarp super-sweetcorn is dependent on breaking the a1-sh2 tight genetic linkage, which occurs at a very low frequency of A1Sh2 . A1Sh2 ) and a female white shrunken2 super-sweetcorn (white-shrunken seed), ‘Tims-white’ ( a1sh2 . a1sh2 ), was conducted. Subsequent self-pollination based on purple-pericarp-shrunken kernels identified a small frequency (0.08%) of initial heterozygous F3 segregants ( A1a1 . sh2sh2 ) producing a fully sh2 cob with a purple-pericarp phenotype, enabled by breaking the close genetic linkage between the a1 and sh2 genes. Resulting rounds of self-pollination generated a F6 homozygous purple-pericarp super-sweetcorn ( A1A1 . sh2sh2 ) line, ‘Tim1’. Genome sequencing revealed a recombination break between the a1 and yz1 genes of the a1-yz1-x1-sh2 multigenic interval, with the sequence pattern of ‘Tim1’ similar to the ‘Costa Rica’ parent, and after the linkage break, similar to the ‘Tims-white’ parent. The novel purple-pericarp super-sweetcorn produced a similar concentration of anthocyanin and sugar as in its purple-pericarp maize and white super-sweetcorn parents, respectively, potentially adding a broader range of health benefits than currently exists with standard yellow/white sweetcorn.

The environment is polluted day by day and it is very much expensive to remediate the environmental pollutants by physicochemical process. Therefore, using plants as a process to remediate pollutants is essential. In this study, phytoremediation of root and leaf tissues of Indian mustard ( Brassica juncea ), rice ( Oryza sativa ) and wheat ( Triticum aestivum ) against three most environment pollutants viz . lead (Pb), chromium (Cr) and cadmium (Cd) of Buriganga riverbank soil of Dhaka city, Bangladesh were assessed. The highest amount of Pb was found in the leaf (11.6755 ±1.9860 mg/kg dry weight) and root (51.4251 ±5.0320 mg/kg dry weight) of B. juncea . However, the highest amount of Cr was found in the leaf (5.9871±0.9032 mg/kg dry weight) of B. juncea ; and in the root (46.4739±2.2920 mg/kg dry weight) of O. sativa respectively. Although the highest amount (0.9624±0.0920 mg/kg dry weight) of Cd was found in the leaf of B. juncea ; the amount of Cd in the root was approximately same in all the three plants. This research also found more amounts of heavy metals compared to other studies using Indian mustard, rice and wheat against the three most environmental pollutants viz., Pb, Cr and Cd. Moreover, this study revealed that B. juncea is the highest hyperaccumulator species regarding Pb, Cr and Cd accumulation and can be used to clean up the polluted Buriganga riverbank soil.

Buriganga, an economically important river of Dhaka, Bangladesh, is highly polluted by different toxic heavy metals. In this study, phytoremediation of EMS induced Indian mustard ( Brassica juncea L) genotypes against three pollutants viz . lead (Pb), chromium (Cr) and cadmium (Cd) of Buriganga riverbank soil was assessed in field condition. Among 1-, 2- and 3% EMS induced genotypes, better seed germination rate, germination speed and plant survival rate were observed in 1% EMS induced genotype, BE21. The highest concentration of Pb, Cr and Cd were also obtained in the leaf of BE21 genotype and therefore was considered as a super-hyperaccumulator genotype. Concentration of Pb in the next generation of this genotype was approximately two-fold higher in the root (91.53±6.59 mg/kg dry weight, DW); three-fold higher in the shoot (33.31±1.01 mg/kg DW) and leaf (28.35±3.61 mg/kg DW), and more in the fruit (5.59±0.93 mg/kg DW) than the control. Concentration of Cr was approximately two-fold in the root (57.02±3.24 mg/kg DW), shoot (18.51±1.36 mg/kg DW) and leaf (14.98±2.01 mg/kg DW), and more in the fruit (6.15±1.92 mg/kg DW) of BE21 genotype compared to the control. Cd concentration was more in the root (1.96±0.92 mg/kg DW), leaf (0.52±0.32 mg/kg DW) and fruit (0.19±0.02 mg/kg DW) and less in the shoot (0.19±0.01 mg/kg DW) of BE21 genotype than the control. Root, shoot, leaf and fruit of BE21 altogether accumulated 98-, 73- and 87% Pb, Cr and Cd, respectively and can thus be utilized to remove heavy metals of Buriganga River. As like root, shoot and leaf, fruit also accumulated heavy metals; hence those plants which are used in phytoremediation should not be used as food or fodder. To the best of our knowledge, this is the first report of developing EMS induced hyperaccumulator genotype of B. juncea for phytoremediation of Buriganga riverbank soil of Bangladesh.