Overexpression of <Emphasis Type="Italic">AtATM3</Emphasis> in <Emphasis Type="Italic">Brassica juncea</Emphasis> confers enhanced heavy metal tolerance and accumulation |
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Authors: | Mohammed Shafi Ullah Bhuiyan Sung Ran Min Won Joong Jeong Sayeda Sultana Kwan Sam Choi Youngsook Lee Jang R Liu |
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Institution: | (1) School of Science and Education, University of the Sunshine Coast, Maroochydore DC, QLD, 4558, Australia;(2) Agri-Science Queensland, University of the Sunshine Coast, Maroochydore DC, QLD, 4558, Australia; |
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Abstract: | The eucalypt Corymbia torelliana × C. citriodora is planted widely in India, Brazil and Australia although plantation establishment has been limited by inadequate seed supply
and low amenability to propagation via cuttings. This study optimised node culture and organogenic culture methods for in
vitro propagation of Corymbia hybrids by identifying explant position (topophysic) effects on rooting, shoot elongation and shoot proliferation. Strong,
negative morphogenic gradients in shoot elongation and proliferation capacity were evident from the cotyledonary node to the
fourth or fifth node of seedlings when their nodes were transferred to node culture (without benzyladenine). These topophysic
effects were related to differences in rooting capacity of individual nodes. Root formation in node culture was associated
with formation of long multi-nodal axillary shoots, and so higher rooting of shoots from the cotyledonary node or first true-leaf
node was associated with higher shoot proliferation. However, all nodes were equally capable of shoot proliferation in organogenic
culture (with 2.2 μM benzyladenine), where rooting and rapid stem elongation did not occur. Most shoots (61–100%) from both
node culture and organogenic culture were converted to plantlets, with plantlet conversion and primary root number not differing
significantly among explant node positions. The strong topophysic effect in node culture, combined with the lack of a topophysic
effect in organogenic culture, provides for an optimised clonal propagation system based on segregation of nodes from the
same seedling into separate node and organogenic culture pathways. |
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