Morphological changes during juvenile-to-adult phase transition in sorghum

• Published in: Planta Vol. 250; no. 5; pp. 1557 - 1566
• Main Authors: Hashimoto, Shumpei, Tezuka, Takahiro, Yokoi, Shuji
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Science + Business Media 01.11.2019; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: Agriculture; Biomedical and Life Sciences; Breeding success; Ecology; Food sources; Forestry; Gene Expression Regulation, Plant; Genetic markers; Leaves; Life Sciences; Markers; Meristem - anatomy & histology; Meristem - genetics; Meristems; MicroRNAs - genetics; miRNA; Morphology; ORIGINAL ARTICLE; Phase transitions; Plant Leaves - anatomy & histology; Plant Leaves - genetics; Plant Sciences; Plants (botany); Reproduction; RNA, Plant - genetics; Sorghum; Sorghum - anatomy & histology; Sorghum - genetics; Trichomes; Trichomes - anatomy & histology; Trichomes - genetics; Sorghum; Gene expression analysis; Juvenile-to-adult phase transition; MicroRNA156/172
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-019-03251-x

The juvenile-to-adult (JA) phase transition is an important event for optimizing vegetative growth and reproductive success in plants. Among the Poaceae crops, which are a vital food source for humans, studies of the JA phase transition have been restricted to rice and maize. We studied the morphological and genetic changes that occur during the early development of sorghum and found that dramatic changes occur in shoot architecture during the early vegetative stages. Changes were observed in leaf size, leaf shape, numbers of trichomes, and size of the shoot apical meristem. In particular, the length/width ratios of the leaf blades in the fifth and upper leaves were completely different from those of the second to fourth leaves. The fifth and upper leaves have trichomes on their adaxial sides, which were absent on the lower leaves. We also analyzed expression of two microRNAs that are known to be molecular markers of the JA phase transition and found that expression of miR156 was highest in the second to fourth leaves and then was gradually down-regulated, whereas miR172 expression followed the opposite pattern. These results suggest that in sorghum, the second and third leaves represent the juvenile phase, the fourth and fifth leaves are in the transition stage, and the sixth and upper leaves are in the adult phase. Thus, the JA phase transition occurs during the fourth and fifth leaf stages. These findings are expected to be useful for understanding the early development of sorghum.