Change of shoot architecture during juvenile-to-adult phase transition in soybean

Abstract

Juvenile-to-adult phase change is an indispensable event which guarantees a successful life cycle. Phase change has been studied in maize, Arabidopsis and rice, but is mostly unknown in other species. Soybean/Fabaceae plants undergo drastic changes of shoot architecture at the early vegetative stage including phyllotactic change and leaf type alteration from simple to compound. These characteristics make soybean/Fabaceae plants an interesting taxon for investigating vegetative phase change. Following the expansion of two cotyledons, two simple leaves simultaneously emerge in opposite phyllotaxy. The phyllotaxy of the third and fourth leaves is not fixed; both opposite and distichous phyllotaxis are observed within the same population. Leaves were compound from the third leaf. But the third leaf was rarely simple. Morphological and quantitative changes in early vegetative phase were recognized in leaf size, leaf shape, number of trichomes, stipule size and shape, and shoot meristem shape. Two microRNA genes, miR156 and miR172, are known to be associated with vegetative phase change. Examination of the expression level revealed that miR156 expression was high in the first two leaves and subsequently down-regulated, and that of miR172 showed the inverse expression pattern. These expression patterns coincided with the case of other species. Taken all data together, the first and second leaves represent juvenile phase, the fifth and upper leaves adult phase, and the third and fourth leaves intermediate stage. Further investigation of soybean phase change would give fruitful understandings on plant development.

Heteroblastic Development of Transfer Cells Is Controlled by the microRNA miR156/SPL Module

“…5B). This result is also in agreement with miR156 levels examined in leaves of Cole's wattle (Acacia colei; Wang et al, 2011), rice (Oryza sativa; Xie et al, 2006Xie et al, , 2012, and soybean (Glycine max; Yoshikawa et al, 2013). In individual leaves, however, miR156 levels increased during maturation of either juvenile or adult leaves (Fig.…”

“…This said, however, it is unknown whether photosynthetic rate of a leaf, and hence phloem loading capacity of minor veins, is similar between mature juvenile and mature adult leaves. In soybean, Yoshikawa et al (2013) showed that photosynthetic rates were comparable between juvenile leaves 1 and 2 and adult leaves 4 to 7, albeit for an unusual increase in leaf 3. In contrast, in rice (Asai et al, 2002) and ivy (Hedera; Bauer and Bauer, 1980), photosynthetic activities are higher in adult leaves compared to juvenile leaves.…”

Jasmonate regulates juvenile-adult phase transition in rice

“…Recently, miR156 and miR172 have been reported as molecular markers for the juvenile-to-adult phase transition in several plant species: the expression level of miR156 is high during the juvenile phase and downregulated during the adult phase, whereas miR172 expression follows the opposite pattern ( Wu and Poethig, 2006;Yoshikawa et al, 2013). Similarly, in rice, the expression level of miR156 was highest in the second leaf and then declined, whereas miR172 expression was repressed in the second leaf but increased with development (as previously reported; see Tanaka et al, 2011;Fig.…”

“…miR156, one of the most abundant microRNAs, is conserved among all land plants, including mosses (Axtell and Bowman, 2008). Recent studies have shown that miR156 accumulation reaches the highest level in seedlings, then decreases gradually as the plant develops, resulting in a gradual increase in target SPL transcripts in a number of herbaceous and woody species (Wu and Poethig, 2006;Chuck et al, 2007;Wang et al, 2009Wang et al, , 2011Wu et al, 2009;Tanaka et al, 2011;Yoshikawa et al, 2013;Hudson et al, 2014). Plants constitutively overexpressing miR156 share common phenotypes in several species, for example, a prolonged juvenile phase, accelerated leaf initiation and delayed flowering (Schwab et al, 2005;Wu and Poethig, 2006;Xie et al, 2006Xie et al, , 2012Zhang et al, 2011;Chuck et al, 2011).…”

Soybean Architecture Plants: From Solar Radiation Interception to Crop Protection

“…The miR156 and miR172, microRNA genes, are known to be associated with vegetative phase change. In soybean, it was shown that miR156 and miR172 genes are involved in the change from juvenile to adult phase, thus demonstrating that the genes play an important role in plant development [13]. In soybean plants overexpressing miR156b, flowering time was suppressed and other genes were negatively regulated [14].…”