Functional identification of anEXPAgene (NcEXPA8) isolated from the treeNeolamarckia cadamba

Abstract

As a class of important cell growth regulators, expansins have been studied for over 20 years. Since Neolamarckia cadamba (Roxb.) Bosser was praised as a 'miraculous tree' at the World Forestry Congress in 1972 due to its rapid growth. A lot of research has been carried out to uncover the underlying mechanisms of this rapid growth. Based on previous findings and our research, we hypothesized that expansins may play an important role in such growth. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that the N. cadamba expansin family member NcEXPA8 is highly expressed in all four young tissues, particularly in the cambium region, suggesting that NcEXPA8 acts as a key regulator of secondary growth in this gene family. Overexpression of NcEXPA8 in Arabidopsis thaliana increased the diameter and height of the main stem. It also promoted interfascicular fiber cell elongation and cell-wall thickness but did not alter the cellulose content in the cell wall. These results suggested that expansins act as activators during secondary fiber cell elongation during tip growth to promote plant growth.

Selection and Validation of Reference Genes for mRNA Expression by Quantitative Real-Time PCR Analysis in Neolamarckia cadamba

“…To date, only two studies on gene expression have been carried out in N . cadamba , and cyclophilin was used as the internal reference for normalization 31 , 33 . However, according to the transcriptome data of leaves, xylem, cambium and phloem, the expression of cyclophilin varied greatly in these samples (unpublished data).…”

“…Neolamarckia cadamba , a member of the Rubiaceae family, is widely distributed in South China and South Asia, and is cultivated due to its inherent economic value in multiple aspects 31 . It has been praised as “a miraculous tree” since the World Forest Congress in 1972 due to its fast growth 32 , 33 , reaching heights of 17 m and trunk diameters of 25 cm within 9 years of growth under normal conditions 34 . Therefore, it is a good choice to use N .…”

Internal Reference Gene Selection under Different Hormone Stresses in Multipurpose Timber Yielding Tree Neolamarckia cadamba

“…Plant hormones and external stimuli (such as light, drought, hormones, salt stress, and hypoxia) affect the expression of expansin genes [32]. Therefore, in order to detect differences among different internal reference genes used in data normalization, the relative expression of NcEXPA8 [17] in the buds, leaves, and cambium regions of N cadamba under different hormone stresses was evaluated. According to the results of RefFinder analysis, the most stable reference gene (combination) and the most unstable reference gene were selected as internal controls, respectively.…”

“…N. cadamba, a member of the Rubiaceae family, is widely distributed throughout South Asia and South China [17]. It has received high praise in the Philippines, where it has been described as "a gem of a tree", and was universally accepted as "a miraculous tree" at the World Forestry Congress in 1972 because of its fast growth [18].…”

The complete chloroplast genome of the miracle treeNeolamarckia cadambaand its comparison in Rubiaceae family

“…With this evidence, it is no wonder that N. cadamba has been an ayurvedic remedy in many Indian traditional medicines [10]. In south China, N. cadamba is currently being cultivated for urban greening, building materials, pulp production and animal feed ingredients [11]. Hence, it is also known as the 'miracle tree'.…”