Compound leaves, that consist of multiple independent units called leaflets, show wide diversity in patterning, ranging from trifoliolate, palmate, pinnate to higher-ordered forms. There is agreement that the proximodistal expression patterns of morphogenetic regulators are associated with the compound leaf patterning. However, the mechanisms by which such patterns are established, maintained, and regulated, as well as their functional relationships with the sequential progression of leaflet formation are largely unknown.
In a study published in Nature Communications, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) elucidated the molecular mechanism regulating the spatiotemporal initiation pattern of cotyledon primordia in pinnate compound leaves in legumes for the first time, using chickpea as a research object.
By using scanning electron microscopy (SEM), the researchers firstly resolved the whole process of early compound leaf development in wild type chickpea. They clarified that the initiation order of lateral mesophyll primordia along the basal axis of compound leaf primordium (CLP) was typical apical-wise.
The researchers cloned the naturally occurring mutant multi-pinnate leaf (mpl1) of chickpea that has been known in the literature for more than 60 years. Through BSA-Seq, linkage analysis, and genotyping of multiple independent alleles, they identified Ca_02268 as the gene responsible for the mpl1 leaf phenotype.
By analyzing naturally occurring mutants multi-pinnate leaf1 (mpl1) that develop higher-ordered pinnate leaves with more than forty leaflets, the researchers showed that MPL1 encoding a C2H2-zinc finger protein sculpted a morphogenetic gradient along the proximodistal axis of the early leaf primordium, thereby conferring the acropetal leaflet formation.
The findings suggested that MPL1 not only played an essential role in promoting a differentiated fate of the leaflet primordia through repressing the CaLFY expression, but may also have a significant function in promoting leaflet blade expansion through regulating cell division.
The study revealed an important regulatory mechanism underlying the patterning of chickpea pinnules, providing new clues for deciphering the molecular mechanisms underlying the morphological patterning of plant pinnae.
"It also provides important theoretical guidance and genetic resources for molecular breeding and genetic improvement of chickpea,” said CHEN Jianghua of XTBG.
Contact
CHEN Jianghua Ph.D Principal Investigator
Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, Yunnan, China
E-mail: jhchen@xtbg.ac.cn
First published: 7 December 2023
