Development of Rice Leaves:How Histocytes Modulate Leaf Polarity Establishment

An ideal leaf shape is beneficial to the yield of rice.Molecular understanding of the leaf primordia and polarity establishment plays a significant role in exploring the genetic regulatory network of leaf morphogenesis.In recent years,researchers have cloned an array of coding genes and a few non-coding small RNAs involved in rice leaf development through regulating the development of leaf primordia,vascular bundles,sclerenchyma cells,bulliform cells,cell walls and epidermis cells.These genes and their interactions play critical roles in rice leaf development through the determination and regulatory role in gene expression,and their coordination with other genetic networks or signal pathways.But the relationship among these genes is poorly defined and the underlying network is still unclear.In this review,we introduced the regulatory pathways of leaf primordium development and leaf polarity establishment,mainly the relationship between cell development mechanism and leaf polarity establishment,focusing on how leaf tissue affects leaf shape.Hopefully,the regulation network reviewed here has immediate implications for future research and genomic design breeding.

Gene expression,transcription factor binding and histone modification predict leaf adaxial-abaxial polarity related genes

Leaf adaxial-abaxial(ad-abaxial)polarity is crucial for leaf morphology and function,but the genetic machinery governing this process remains unclear.To uncover critical genes involved in leaf ad-abaxial patterning,we applied a combination of in silico prediction using machine learning(ML)and experimental analysis.A Random Forest model was trained using genes known to influence ad-abaxial polarity as ground truth.Gene expression data from various tissues and conditions as well as promoter regulation data derived from transcription factor chromatin immunoprecipitation sequencing(ChIP-seq)was used as input,enabling the prediction of novel ad-abaxial polarity-related genes and additional transcription factors.Parallel to this,available and newly-obtained transcriptome data enabled us to identify genes differentially expressed across leaf ad-abaxial sides.Based on these analyses,we obtained a set of 111 novel genes which are involved in leaf ad-abaxial specialization.To explore implications for vegetable crop breeding,we examined the conservation of expression patterns between Arabidopsis and Brassica rapa using single-cell transcriptomics.The results demonstrated the utility of our computational approach for predicting candidate genes in crop species.Our findings expand the understanding of the genetic networks governing leaf ad-abaxial differentiation in agriculturally important vegetables,enhancing comprehension of natural variation impacting leaf morphology and development,with demonstrable breeding applications.

From genes to networks: The genetic control of leaf development

Substantial diversity exists for both the size andshape of the leaf,the main photosynthetic organofflowering plants.The two major forms of leaf aresimple leaves,in which the leaf blade is undivided,and compound leaves,which comprise severalleaflets.Leaves form at the shoot apical meristemfrom a group of undifferentiated cells,whichfirstestablish polarity,then grow and differentiate.Each of these processes is controlled by a com-bination of transcriptional regulators,microRNAsand phytohormones.The present review docu-ments recent advances in our understanding ofhow these various factors modulate the develop-ment of both simple leaves(focusing mainly on themodel plantArabidopsis thaliana)and compoundleaves(focusing mainly on the model legumespeciesMedicago truncatula).