Abstract
The change of pectin epitopes during procambium–cambium continuum development was investigated by immunolocalization in poplar. The monoclonal antibody JIM5 labels homogalacturonan (HGA) with a low degree of esterification, and the monoclonal antibody JIM7 labels HGA with a high degree of methyl-esterification. Arabinan, rather than galactan, and HGA with low degree of esterification were located in the cell walls of procambial, while HGA with a low degree of esterification was located in the tangential walls, and galactan was located in both the tangential and radial walls of procambial, yet nearly no arabinan was located in the tangential walls of the cambial cells. The changes in pectin distribution took place when periclinal divisions appeared within a procambial trace. The distribution difference of pectin epitopes was also present in procambium–cambium derivatives. The arabinan existed in all cell walls of primary xylem, but was absent from the tangential walls of secondary xylem cells. The galactan existed only in mature primary phloem. Furthermore, 19 pectin methylesterases (PMEs) genes were identified by RNA sequencing, six genes presented highly differentially and were supposed to be involved in the cell wall esterification process. The results provide direct evidence of the dynamic changes of pectin epitopes during the development of the procambium–cambium continuum in poplar.
Highlights
During the colonization of land, vascular plants acquired the ability to mechanically support the plant body and maintain vigorous growth in the atmosphere [1]
Examination of serial sections of apex and stem tissues showed that the procambium–cambium meristematic continuum in P. tomentosa could be subdived into procambium, initiating layer, metacambium and cambium, similar to P. deltoids [5,6]
The study firstly traced the change of pectin side chains during the development of the primary–secondary vascular system in poplar
Summary
During the colonization of land, vascular plants acquired the ability to mechanically support the plant body and maintain vigorous growth in the atmosphere [1]. The vascular system of most vascular plant species includes the primary and the secondary vascular systems, which differentiate from procambium and cambium, respectively. Procambium and cambium occur in a developmental community [2,3,4,5]. In Populus deltoides, the community is further subdivided into procambium, initiating layer, metacambium and cambium according to the anatomical structure [6,7,8]. Cell growth and differentiation are accompanied by quantitative and qualitative changes in the composition of cell wall polysaccharides [9,10,11]. Pectin is a major component of the primary cell walls of plants and encompasses a range of galacturonic acid-rich polysaccharides [12]. Homogalacturonan (HGA), rhamnogalacturonan-I (RG-I) and rhamnogalacturonan-II (RG-II), occur in all primary cell walls [13]. Developments in analytical techniques and the application of anti-pectin probes have begun to place the structural complexity of pectin in cell biological and developmental contexts [14]
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